Ready for the future

Swift is brand spanking new. How can we possibly be expected to write idiomatic code? On the other hand, Objective-C has been around for more than thirty years. We know what it looks like and feels like. The Objective-C of our iOS youth is very different than today’s Objective-C. Seen in this light, Swift is more evolutionary than you might think. In this talk we’ll look at Swift code in the light of the code of Objective-C and other languages that have come before it.

Daniel Steinberg http://dimsumthinking.com

Transcript

4. Handwritten Slides?
5. Boring Handwritten Slides
6. This Talk Sucks
7. I'm Already nodding off
8. Not Even Speaker Colleagues Everyone Parents
9. Let's start
10. Recipe
11. Eugenia Cheng: "Cakes, Custard + Category Theory"
12. Eugenia Cheng: "Cakes, Custard + Category Theory"
13. Eugenia Cheng: "Cakes, Custard + Category Theory" I hope this talk isn't about Monads and Functors.
14. Recipe
15. Lasagne
16. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan
17. Context
18. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan
19. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan
20. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan
21. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan Béchamel is one of the mother sauces
22. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan Bechamel Sauce » Butter » Flour » Milk » Salt and Pepper
23. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan Bechamel Sauce » Butter » Flour » Milk » Salt and Pepper
24. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan Bechamel Sauce » Butter » Flour » Milk » Salt and Pepper Context matters
25. Context matters
26. Context matters
27. An Obj-C example
28. An Obj-C example
29. An Obj-C example
30. The model
31. - (NSTimeInterval)elapsed Time { NSDate *now = [[NSDate alloc] init]; NSTimeInterval elapsed Time = [now timeIntervalS inceDate:self.startTime]; return elapsedTime; }
32. - (NSTimeInterval)elapsed Time { NSDate *now = [[NSDate alloc] init]; NSTimeInterval elapsed Time = [now timeIntervalS inceDate:self.startTime]; return elapsedTime; }
33. - (NSTimeInterval)elapsed Time { NSDate *now = [[NSDate alloc] init]; NSTimeInterval elapsed Time = [now timeIntervalS inceDate:self.startTime]; return elapsedTime; }
34. - (NSTimeInterval)elapsed Time { NSDate *now = [[NSDate alloc] init]; NSTimeInterval elapsed Time = [now timeIntervalS inceDate:self.startTime]; return elapsedTime; }
35. - (NSTimeInterval)elapsed Time { NSDate *now = [[NSDate alloc] init]; NSTimeInterval elapsed Time = [now timeIntervalS inceDate:self.startTime]; return elapsedTime; }
36. - (NSTimeInterval)elapsed Time { return [self.startTime timeIntervalSinceNow]; }
37. - (NSTimeInterval)elapsed Time { return [self.startTime timeIntervalSinceNow]; }
39. - (NSTimeInterval)elapsed Time { return -[self.startTime timeIntervalSinceNow]; }
40. - (NSTimeInterval)elapsed Time { return -[self.startTime timeIntervalSinceNow]; }
41. - (NSTimeInterval)elapsed Time { return [self.startTime timeIntervalUntilNow]; }
42. #import <Foundation/Foundation.h> @interface NSDate (TimerCalculations) - (NSTimeInterval)timeIntervalUntilNow; @end
43. #import <Foundation/Foundation.h> @interface NSDate (TimerCalculations) - (NSTimeInterval)timeIntervalUntilNow; @end
44. #import "NSDate+TimerCalculations.h" @implementation NSDate (TimerCalculations) - (NSTimeInterval) timeIntervalUntilNow { return - [self timeIntervalSinceNow]; } @end
45. #import "NSDate+TimerCalculations.h" @implementation NSDate (TimerCalculations) - (NSTimeInterval) timeIntervalUntilNow { return - [self timeIntervalSinceNow]; } @end
46. #import "NSDate+TimerCalculations.h" @implementation NSDate (TimerCalculations) - (NSTimeInterval) timeIntervalUntilNow { return - [self timeIntervalSinceNow]; } @end
47. #import "NSDate+TimerCalculations.h" @implementation NSDate (TimerCalculations) - (NSTimeInterval)dst_timeIntervalUntilNow { return - [self timeIntervalSinceNow]; } @end
48. Context
49. Clean
50. Clear
51. Lasagne
52. - (NSTimeInterval)elapsedTime { return [self.startTime timeInterval UntilNow]; }
53. - (NSTimeInterval)elapsedTime { return startTime.timeIntervalUntilNow }
54. - (NSTimeInterval)elapsedTime { return startTime.timeIntervalUntilNow } Exactly
55. - (NSTimeInterval)elapsedTime { return startTime.timeIntervalUntilNow } Let's get to some swift
56. - (NSTimeInterval)elapsedTime { return startTime.timeIntervalUntilNow } Show me some clever unreadable code
57. - (NSTimeInterval)elapsedTime { return startTime.timeIntervalUntilNow } Let's see some Generics and Custom operators
58. The model in Swift
59. struct Timer { let startTime = NSDate() var elapsedTime: NSTimeInterval { return startTime.timeIntervalUntilNow } }
60. struct Timer { let startTime = NSDate() var elapsedTime: NSTimeInterval { return startTime.timeIntervalUntilNow } }
61. struct Timer { let startTime = NSDate() var elapsedTime: NSTimeInterval { return startTime.timeIntervalUntilNow } }
62. struct Timer { let startTime = NSDate() var elapsedTime: NSTimeInterval { return startTime.timeIntervalUntilNow } }
63. } } extension NSDate { var timeIntervalUntilNow: NSTimeInterval { return -timeIntervalSinceNow } }
64. extension NSDate { var timeIntervalUntilNow: NSTimeInterval { return -timeIntervalSinceNow } }
65. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan Bechamel Sauce » Butter » Flour » Milk » Salt and Pepper
66. Clean
67. Compact
68. Clear
69. UmmM, Daniel
70. You Started with Obj-C
71. And converted it to Swift
72. What about Real Swift
73. Show me Map, Filter, reduce!
74. Silly Example
75. App Sales
76. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
77. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
78. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
79. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
80. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
81. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
82. import GameplayKit struct AppSales: SequenceType { let numberOfDays: Int let randomDistribution = GKGaussianDistribution(lowestValue: 0, highestValue: 10) func generate() -> Any Generator<Int> { var count = 0 return anyGenerator({ if count++ < self .numberOfDays { return self .randomDistribution.nextInt() } else { return nil } }) } }
83. let lastWeeksSales = AppSales(numberOfDays: 7) for dailySales in lastWeeksSales { print(dailySales) }
84. AppSales is a SequenceType
85. for in
86. let lastWeeksSales = AppSales(numberOfDays: 7) for dailySales in lastWeeksSales { print(dailySales) }
87. 6 5 6 4 6 4 3 let lastWeeksSales = AppSales(numberOfDays: 7) for dailySales in lastWeeksSales { print(dailySales) }
88. AppSales is a SequenceType
89. map, filter, reduce, flatmap, …
90. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
91. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
92. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
93. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
94. [6.964999999999999, 8.357999999999999, 5.572, 6.964999999999999, 5.572, 4.178999999999999, 4.178999999999999] let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
95. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
96. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
97. Context
98. let lastWeeksSales = AppSales(numberOfDays: 7) let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * 1.99 * 0.70 }
99. let lastWeeksSales = AppSales(numberOfDays: 7) let unitPrice = 1.99 let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * unitPrice * 0.70 }
100. let lastWeeksSales = AppSales(numberOfDays: 7) let unitPrice = 1.99 let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * unitPrice * 0.70 }
101. let lastWeeksSales = AppSales(numberOfDays: 7) let unitPrice = 1.99 let sellersPercentage = 0.70 let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * unitPrice * sellersPercentage }
102. let lastWeeksSales = AppSales(numberOfDays: 7) let unitPrice = 1.99 let sellersPercentage = 0.70 let lastWeeksRevenues = lastWeeksSales.map{dailySales in Double(dailySales) * unitPrice * sellersPercentage }
103. let lastWeeksSales = AppSales(numberOfDays: 7) let unitPrice = 1.99 let sellersPercentage = 0.70 func revenuesForCopies Sold(numberOfCopies: Int) -> Double { return Double(number OfCopies) * unitPrice * sellersPercentage } let lastWeeksRevenues = lastWeeksSales.map{dailySales in revenuesForCopiesSold(dailySales) }
104. let lastWeeksRevenues = lastWeeksSales.map{dailySales in revenuesForCopiesSold(dailySales) }
105. let lastWeeksRevenues = lastWeeksSales.map{revenuesForCopies Sold($0) }
106. let lastWeeksRevenues = lastWeeksSales.map(revenuesForCopies Sold)
107. let lastWeeksRevenues = lastWeeksSales.map(revenuesForCopies Sold)
108. Adjust the distribution
109. Wider
110. let randomDistribution = GKGaussianDistribution(lowestValue: -5, highestValue: 15)
111. Negatives count as 0
112. Could filter copies > 0
113. let lastWeeksRevenues = lastWeeksSales.filter{$0 > 0} .map(revenuesForCopiesSold)
114. Filter can change size of array
115. Could map negatives -> 0
116. let lastWeeksRevenues = lastWeeksSales.map{$0 > 0 ? $0 : 0} .map(revenuesForCopiesSold)
117. "Doctor it hurts when I do that."
118. "Don't do that."
119. let lastWeeksRevenues = lastWeeksSales.map{$0 > 0 ? $0 : 0} .map(revenuesForCopiesSold)
120. func negativeNumbersToZero (number: Int) -> Int { return max(0, number) } let lastWeeksRevenues = lastWeeksSales.map(negativeNumbersToZero) .map(revenuesForCopiesSold)
121. Good News
122. let lastWeeksRevenues = lastWeeksSales.map(negativeNumbersToZero) .map(revenuesForCopiesSold)
123. let lastWeeksRevenues = lastWeeksSales.map(negativeNumbersToZero) .map(revenuesForCopiesSold)
124. We'll come back to the Lasagne.
125. First, the béchamel.
126. func revenues ForCopiesSold(numberOfCopies: Int) -> Double { return Double(numberOfCopies) * unitPrice * sellersPercentage }
127. func revenues ForCopiesSold(numberOfCopies: Int) -> Double { return Double(numberOfCopies) * unitPrice * sellersPercentage }
128. typealias USDollars = Double func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage }
129. typealias USDollars = Double func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage } func toThe NearestPenny(dollarAmount: USDollars) -> USDollars { return round(dollarAmount * 100)/100 }
130. typealias USDollars = Double func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage } func toThe NearestPenny(dollarAmount: USDollars) -> USDollars { return round(dollarAmount * 100)/100 } func revenues InDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return toTheNearestPenny(revenuesForCopiesSold (numberOfCopies)) }
131. typealias USDollars = Double func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage } func toThe NearestPenny(dollarAmount: USDollars) -> USDollars { return round(dollarAmount * 100)/100 } func revenues InDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return toTheNearestPenny(revenuesForCopiesSold (numberOfCopies)) }
132. typealias USDollars = Double func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage } func toThe NearestPenny(dollarAmount: USDollars) -> USDollars { return round(dollarAmount * 100)/100 } func revenues InDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return toTheNearestPenny(revenuesForCopiesSold (numberOfCopies)) }
133. typealias USDollars = Double func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage } func toThe NearestPenny(dollarAmount: USDollars) -> USDollars { return round(dollarAmount * 100)/100 } func revenues InDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return toTheNearestPenny(revenuesForCopiesSold (numberOfCopies)) }
134. Backwards
135. func revenues InDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return toTheNearestPenny(revenuesForCopiesSold (numberOfCopies)) }
136. Method chaining
137. Extensions
138. Extensions UmmM, Daniel
139. Extensions How did your talk get accepted?
140. Extensions No Generics.
141. Extensions No Custom Operators
142. Custom Operator
143. Custom Operator What?
144. Custom Operator
145. Custom Operator And Generics?
146. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
147. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
148. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
149. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
150. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
151. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
152. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
153. Clearly …
154. Context
155. infix operator » {associativity left} func »<T, U>(input: T, transform: T -> U) -> U { return transform(input) }
156. Use it
157. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » toTheNearestPenny }
158. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » toTheNearestPenny }
159. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » toTheNearestPenny }
160. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » toTheNearestPenny }
161. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » toTheNearestPenny }
162. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » toTheNearestPenny }
163. Back to the Lasagne
164. let lastWeeksRevenues = lastWeeksSales .map(negativeNumbersToZero) .map(revenuesInDollarsForCopiesSold)
165. map is like -
166. Move map
167. let lastWeeksRevenues = lastWeeksSales .map(negativeNumbersToZero) .map(revenuesInDollarsForCopiesSold)
168. func replaceNegativeSalesWithZeroSales(sales: [Int]) -> [Int] { return sales.map(negativeNumbersToZero) } func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollarsFor CopiesSold) }
169. Types Match
170. func replaceNegativeSalesWithZeroSales(sales: [Int]) -> [Int] { return sales.map(negativeNumbersToZero) } func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollarsFor CopiesSold) }
171. Types Don't Match
172. let lastWeeksSales = AppSales(numberOfDays: 7) func replaceNegativeSalesWithZeroSales(sales: [Int]) -> [Int] { return sales.map(negativeNumbersToZero) } func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollarsFor CopiesSold) }
173. func anArrayOfDailySales(rawSales: AppSales) -> [Int] { return rawSales.map{$0} }
174. Chain them together
175. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
176. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
177. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
178. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
179. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
180. Lasagne
181. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan
182. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
183. We don't do this
184. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce ̣ Butter ̣ Flour ̣ Milk ̣ Salt and Pepper » Grated parmesan
185. let lastWeeksRevenues = lastWeeksSales .map{$0 > 0 ? $0 : 0} .map{round(Double($0) * unitPrice * sellersPercentage * 100)/100 }
186. We zoom in
187. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan
188. Lasagne » Bolognese sauce » Lasagne sheets » Béchamel sauce » Grated parmesan Bechamel Sauce » Butter » Flour » Milk » Salt and Pepper
189. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
190. let lastWeeksRevenues = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales
191. = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollars ForCopiesSold) }
192. = lastWeeksSales » anArrayOfDailySales » replaceNegativeSalesWithZeroSales » calculateRevenuesFromSales func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollarsForCopiesSold) }
193. evenuesFromSales(sales: [Int]) -> [USDollars] { s.map(revenuesInDollarsForCopiesSold) func revenuesInDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » roundedToTheNearestPenny }
194. evenuesFromSales(sales: [Int]) -> [USDollars] { s.map(revenuesInDollarsForCopiesSold) func revenuesInDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » roundedToTheNearestPenny }
195. uesInDollarsForCopiesSold(numberOfCopies: Int) -> USDollars { numberOfCopies » revenuesForCopiesSold » roundedToTheNearestPenny func revenuesForCopiesSold(numberOfCopies: NumberOfCopies) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage }
196. func revenuesForCopiesSold(numberOfCopies: NumberOfCopies) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage }
198. Clean
199. Clear
200. Testable
201. Context
202. And yet …
203. »
204. func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage }
205. func revenues ForCopiesSold(numberOfCopies: Int) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage }
206. typealias NumberOfCopies = Int func revenues ForCopiesSold(numberOfCopies: Number OfCopies) -> USDollars { return Double(numberOfCopies) * unitPrice * sellersPercentage }
207. extension NumberOfCopies { private func revenuesForCopiesSold() -> USDollars { return Double(self) * unitPrice * sellersPercentage } }
208. extension NumberOfCopies { private func revenuesForCopiesSold() -> USDollars { return Double(self) * unitPrice * sellersPercentage } }
209. extension NumberOfCopies { private func revenuesForCopiesSold() -> USDollars { return Double(self) * unitPrice * sellersPercentage } }
210. extension NumberOfCopies { private func revenuesForCopiesSold() -> USDollars { return Double(self) * unitPrice * sellersPercentage } }
211. extension USDollars { private func roundedToTheNearestPenny() -> USDollars { return round(self * 100)/100 } }
212. extension USDollars { private func roundedToTheNearestPenny() -> USDollars { return round(self * 100)/100 } }
213. extension USDollars { private func roundedToTheNearestPenny() -> USDollars { return round(self * 100)/100 } }
214. func revenuesInDollarsForCopiesSold(number OfCopies: Int) -> USDollars { return numberOfCopies » revenuesForCopiesSold » roundedToTheNearestPenny }
215. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
216. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
217. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
218. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
219. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
220. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
221. extension NumberOfCopies { private func revenuesIn DollarsForCopiesSold() -> USDollars { return self.revenues ForCopiesSold().roundedToTheNearestPenny () } }
222. 7.revenuesInDollarsForCopiesSold()
223. 7.revenuesInDollarsForCopiesSold() 9.75
224. extension NumberOfCopies { private func revenues InDollarsForCopiesSold() -> USDollars { return revenues ForCopiesSold().roundedToTheNearestPenny () } }
225. Removed »
226. That's Béchamel
227. What about Lasagne?
228. func replace NegativeSalesWithZeroSales(sales: [Int]) -> [Int] { return sales.map(negativeNumbersToZero) }
229. Where?
230. extension [NumberOfCopies] { }
231. Can't
232. extension [Int] { }
233. Still Can't
234. Rich Hickey's Trolley
235. Not bad for map()
236. Wait a minute
237. What does this have to do with Lasagne?
238. Everything at once
239. Fancy made to order
240. Back to map()
241. Combine
242. func anArrayOf DailySales(rawSales: AppSales) -> [Int] { return rawSales.map{$0} } func replace NegativeSalesWithZeroSales(sales: [Int]) -> [Int] { return sales.map(negativeNumbersToZero) } func calcu lateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollarsForCopiesSold) }
243. func processEndToEnd(sales: AppSales) -> USDollars { return sales.map(transform: Int -> U) }
244. Combine
245. func anArrayOf DailySales(rawSales: AppSales) -> [Int] { return rawSales.map{$0} } func replace NegativeSalesWithZeroSales(sales: [Int]) -> [Int] { return sales.map(negativeNumbersToZero) } func calcu lateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollarsForCopiesSold) } func processEndToEnd(sales: AppSales) -> USDollars { return sales.map(transform: Int -> U) }
246. func processEndToEnd(sales: AppSales) -> USDollars { return sales.map(transform: Int -> U) }
247. This doesn't work
248. func process EndToEnd(sales: AppSales) -> USDollars { return sales .map(negativeNumbersToZero » revenuesInDollarsForCopiesSold) }
249. Types don't match
250. This works …
251. func combinedSteps(input: Int) -> USDollars { return input » negativeNumbersToZero » revenuesInDollarsForCopiesSold } func processEndToEnd(sales: AppSales) -> [USDollars] { return sales.map(combinedSteps) }
252. func combinedSteps(input: Int) -> USDollars { return input » negativeNumbersToZero » revenuesInDollarsForCopiesSold } func processEndToEnd(sales: AppSales) -> [USDollars] { return sales.map(combinedSteps) }
253. func combinedSteps(input: Int) -> USDollars { return input » negativeNumbersToZero » revenuesInDollarsForCopiesSold } func processEndToEnd(sales: AppSales) -> [USDollars] { return sales.map(combinedSteps) }
254. func combinedSteps(input: Int) -> USDollars { return input » negativeNumbersToZero » revenuesInDollarsForCopiesSold } func processEndToEnd(sales: AppSales) -> [USDollars] { return sales.map(combinedSteps) }
255. Want…
256. func processEndToEnd(sales: AppSales) -> [USDollars] { return sales.map(negativeNumbersToZero » revenuesInDollarsForCopiesSold) }
257. The types
258. Overload »
259. func »<T,U,V> (firstFunction: T -> U, secondFunction: U -> V) -> T -> V { return {x in secondFunction(firstFunction(x)) } }
260. func »<T,U,V> (firstFunction: T -> U, secondFunction: U -> V) -> T -> V { return {x in secondFunction(firstFunction(x)) } }
261. func »<T,U,V> (firstFunction: T -> U, secondFunction: U -> V) -> T -> V { return {x in secondFunction(firstFunction(x)) } }
262. func »<T,U,V> (firstFunction: T -> U, secondFunction: U -> V) -> T -> V { return {x in secondFunction(firstFunction(x)) } }
263. func »<T,U,V> (firstFunction: T -> U, secondFunction: U -> V) -> T -> V { return {x in secondFunction(firstFunction(x)) } }
264. let lastWeeksLazyRevenues = lastWeeksSales .map( negativeNumbersToZero » revenuesInDollarsForCopiesSold)
265. let lastWeeksLazyRevenues = lastWeeksSales .map( negativeNumbersToZero » revenuesInDollarsForCopiesSold)
266. let lastWeeksLazyRevenues = lastWeeksSales .map( negativeNumbersToZero » revenuesInDollarsForCopiesSold)
267. let lastWeeksLazyRevenues = lastWeeksSales .map( negativeNumbersToZero » revenuesInDollarsForCopiesSold)
268. map
269. Rich Hickey's Trolley
270. flatmap T -> [U] [T] -> [ U]
271. filter T -> Bool [T] -> [ T]
272. map T -> U [T] -> [ U]
273. reduce U, (U, T) -> U [T] -> U
275. reduce
276. Béchamel
277. Mother Sauce
278. reduce
279. Mother Sauce
280. map with reduce
281. filter with reduce
282. flatmap with reduce
283. Inefficient
284. Instructive
285. reduce
286. reduce U, (U, T) -> U
287. reduce U, (U, T) -> U initial value
288. reduce U, (U, T) -> U step
289. reduce U, (U, T) -> U
290. map with reduce
291. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
292. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
293. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
294. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
295. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
296. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
297. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
298. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
299. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
300. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
301. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
302. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
303. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
304. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
305. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
306. extension SequenceType { func mapUsingReduce <U>(transform: Generator.Element -> U) -> [U] { let initialValue = [U]() func step(accu mulatedValue: [U], nextElement: Generator .Element) -> [U] { return acc umulatedValue + [transform(nextElement)] } return reduce (initialValue, combine: step) } }
307. map with reduce
308. filter with reduce
309. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
310. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
311. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
312. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
313. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
314. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
315. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
316. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
317. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
318. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
319. func filterUsingReduce (includeElement: Generator.Element -> Bool) -> [Generator.Element] { let initialValue = Array<Generator.Element>() func step(accumula tedValue: [Generator.Element], next Element: Generator.Element) -> [Generator .Element] { guard include Element(nextElement) else { return acc umulatedValue } return accumula tedValue + [nextElement] } return reduce(ini tialValue, combine: step) }
320. filter with reduce
321. Use these?
322. func anArrayOfDailySales(rawSales: AppSales) -> [Int] { return rawSales.map{$0} } func replaceNegativeSalesWithZero Sales(sales: [Int]) -> [Int] { return sales.map(negative NumbersToZero) } func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.map(revenuesInDollars ForCopiesSold) }
323. Easy!
324. func anArrayOfDailySales(rawSales: AppSales) -> [Int] { return rawSales.mapUsingReduce{$0} } func replaceNegativeSalesWithZero Sales(sales: [Int]) -> [Int] { return sales.mapUsingReduce(negative NumbersToZero) } func calculateRevenuesFromSales(sales: [Int]) -> [USDollars] { return sales.mapUsingReduce(revenues InDollarsForCopiesSold) }
325. Still need lots of trolleys
327. Performance is worse
328. Compiler Optimizations
329. Transducers
331. One reduce()
332. Chain steps
333. Swift solution?
334. lazy?
335. transducers?
336. Nothing yet
337. Nothing official yet
338. Search: transducers in Swift
339. Idea - chain steps in reduce
340. reduce U, (U, T) -> U
341. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
342. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
343. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
344. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
345. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
346. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
347. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
348. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
349. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
350. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
351. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
352. This seems confusing
353. Are you sure you understand this?
354. Not Even Speaker Colleagues Everyone Parents
355. Not Even Speaker Parents
356. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
357. Start from the last step
358. Use reduce [USDollars], ([USDollars], NumberOfCopies) -> [USDollars] revenuesInDollarsForCopiesSold: NumberOfCopies -> USDollars [NumberOfCopies] -> [USDollars]
359. Use reduce [USDollars], ([USDollars], NumberOfCopies) -> [USDollars] revenuesInDollarsForCopiesSold: NumberOfCopies -> USDollars [NumberOfCopies] -> [USDollars]
360. Use reduce [USDollars], ([USDollars], NumberOfCopies) -> [USDollars] revenuesInDollarsForCopiesSold: NumberOfCopies -> USDollars [NumberOfCopies] -> [USDollars]
361. Use reduce [USDollars], ([USDollars], NumberOfCopies) -> [USDollars] revenuesInDollarsForCopiesSold: NumberOfCopies -> USDollars [NumberOfCopies] -> [USDollars]
362. Use reduce [USDollars], ([USDollars], NumberOfCopies) -> [USDollars] revenuesInDollarsForCopiesSold: NumberOfCopies -> USDollars [NumberOfCopies] -> [USDollars]
363. Use reduce [USDollars], ([USDollars], NumberOfCopies) -> [USDollars] revenuesInDollarsForCopiesSold: NumberOfCopies -> USDollars [NumberOfCopies] -> [USDollars]
364. Chain in another operation
365. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
366. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
367. transducer U, (U, T) -> U U, (U, S) -> U f: S -> T [T] -> U [S] -> U
368. transducer [USDollars], ([USDollars], T) -> [USDollars] [USDollars], ([USDollars], S) -> [USDollars] f: S -> T [T] -> [USDollars] [S] -> [USDollars]
369. transducer [USDollars], ([USDollars], T) -> [USDollars] [USDollars], ([USDollars], S) -> [USDollars] f: S -> T [T] -> [USDollars] [S] -> [USDollars]
370. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], S) -> [USDollars] f: S -> NumberOfCopies [NumberOfCopies] -> [USDollars] [S] -> [USDollars]
371. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], S) -> [USDollars] f: S -> NumberOfCopies [NumberOfCopies] -> [USDollars] [S] -> [USDollars] reduce with revenueInDollarsForCopiesSold
372. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], S) -> [USDollars] f: S -> NumberOfCopies [NumberOfCopies] -> [USDollars] [S] -> [USDollars]
373. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], S) -> [USDollars] negativeNumbersToZero: NumberOfCopies -> NumberOfCopies [NumberOfCopies] -> [USDollars] [S] -> [USDollars]
374. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], S) -> [USDollars] negativeNumbersToZero: Int -> NumberOfCopies [NumberOfCopies] -> [USDollars] [S] -> [USDollars]
375. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], Int) -> [USDollars] negativeNumbersToZero: Int -> NumberOfCopies [NumberOfCopies] -> [USDollars] [Int] -> [USDollars]
376. transducer [USDollars], ([USDollars], NumberOfCopies) -> USDollars [USDollars], ([USDollars], Int) -> [USDollars] negativeNumbersToZero: Int -> NumberOfCopies [NumberOfCopies] -> [USDollars] [Int] -> [USDollars] reduce implementation of the composition
377. transducer
378. One reduce()
379. Chain steps
380. Swift Solution?
381. Not yet
382. Keep your code…
383. Clear
384. Clean
385. Concise
386. Well factored
387. Testable
388. Swift