Secret Swift tour

2018/3/1
try! Swift Conference

Transcript

1. Secret Swift tour 2018/3/1 try! Swift Conference Yuka Ezura
2. var myVariable = 42 myVariable = 50
3. let r = ( ) Void var myVariable = 42 myVariable = 50
4. obj?.myVariable = 50
5. (obj?.myVariable = 50) Optional<Void>
6. (obj?.myVariable = 50) .map { /* do something */ }
7. ! error: Value of optional type 'Int?' not unwrapped; obj?.myVariable + 50
8. infix operator ⭐ func ⭐ (left: Int, right: Int) -> Int { return left + right }aaaaaaa
9. ! error: Value of optional type 'Int?' not unwrapped; obj?.myVariable ⭐ 5 infix operator ⭐ func ⭐ (left: Int, right: Int) -> Int { return left + right }aaaaaaa
10. infix operator ⭐ func ⭐ (left: Int, right: Int) -> Int { return left + right }aaaaaaa
11. precedencegroup FoldedIntoOptionalChaining { assignment: true } :FoldedIntoOptionalChaining infix operator ⭐ func ⭐ (left: Int, right: Int) -> Int { return left + right }aaaaaaa
12. obj?.myVariable ⭐ 5 // => Optional<Int> 1 ⭐ 5 // => Int
13. let myVariable: Int = /* ?? */
14. let myVariable: Int = { while(true) {} }()
15. ! error: Cannot convert value of type 'Never' to specified type 'Int' let naver: Never = unsafeBitCast((),
 to: Never.self) let myVariable: Int = naver
16. let myVariable: Int = { while(true) {} }()
17. (source_file (top_level_code_decl (brace_stmt (pattern_binding_decl (pattern_typed type='Int' (pattern_named type='Int' 'myVariable') (type_ident (component id='Int' bind=Swift.(file).Int))) (call_expr type='Int' location=sample.swift:1:23 range=[sample.swift:1:23 - line:3:3] nothrow arg_labels= (closure_expr type='() -> Int' location=sample.swift:1:23 range=[sample.swift:1:23 - line:3:1] discriminator=0 (parameter_list) (brace_stmt (while_stmt (call_expr implicit type='Int1' location=sample.swift:2:10 range=[sample.swift:2:10 - line:2:15] nothrow arg_labels= (dot_syntax_call_expr implicit type='() -> Int1' location=sample.swift:2:10 range=[sample.swift:2:10 - line:2:15] nothrow (declref_expr implicit type='(Bool) -> () -> Int1' location=sample.swift:2:11 range=[sample.swift: 2:11 - line:2:11] decl=Swift.(file).Bool._getBuiltinLogicValue() function_ref=double) (paren_expr type='(Bool)' location=sample.swift:2:11 range=[sample.swift:2:10 - line:2:15] (call_expr implicit type='Bool' location=sample.swift:2:11 range=[sample.swift:2:11 - line:2:11] nothrow arg_labels=_builtinBooleanLiteral: (constructor_ref_call_expr implicit type='(Int1) -> Bool' location=sample.swift:2:11 range=[sample.swift:2:11 - line:2:11] nothrow (declref_expr implicit type='(Bool.Type) -> (Int1) -> Bool' location=sample.swift:2:11 range=[sample.swift:2:11 - line:2:11] decl=Swift.(file).Bool.init(_builtinBooleanLiteral:) function_ref=single) (type_expr implicit type='Bool.Type' location=sample.swift:2:11 range=[sample.swift:2:11 - line:2:11] typerepr='Bool')) (tuple_expr implicit type='(_builtinBooleanLiteral: Builtin.Int1)' location=sample.swift:2:11 range=[sample.swift:2:11 - line:2:11] names=_builtinBooleanLiteral (boolean_literal_expr type='Builtin.Int1' location=sample.swift:2:11 range=[sample.swift:2:11 - line:2:11] value=true))))) (tuple_expr implicit type='()')) (brace_stmt)))) (tuple_expr type='()' location=sample.swift:3:2 range=[sample.swift:3:2 - line:3:3]))) )) (var_decl "myVariable" type='Int' interface type='Int' access=internal let storage_kind=stored))
18. (closure_expr type='() -> Int' location=sample.swift:1:23 range=[sample.swift:1:23 - line:3:1] discriminator=0 let myVariable: Int = { while(true) {} }()
19. let _: Int = { preconditionFailure() }() let _: Void = { fatalError() }() let _: Never = { while(true) {} }()
20. class SomeClass { lazy var v: Int = { preconditionFailure("Variable '\(#function)' used before being initialized") }()
21. class SomeClass { var v: Int! lazy var v: Int = { preconditionFailure("Variable '\(#function)' used before being initialized") }()
22. Closure
23. let _: (Int) -> Int = { $0 + 1 }
24. func f(x: Int...) -> String { … } let _: (Int...) -> String = f
25. struct SomeType { func f(x: Int) -> String { … } } let _: (Int) -> String = SomeType().f let _: (SomeType) -> (Int) -> String = SomeType.f
26. enum Rank: Int { case ace = 1 case two, three, four, five, six, seven, eight, nine, ten case jack, queen, king } let _: (Int) -> Rank? = Rank.init init?(rawValue: Int)
27. let _: (Int, Int) -> (Int) = (+) let _: (inout Int, Int) -> () = (+=)
28. enum Page { case settings case externalSite(URL) let _: (URL) -> Page = Page.externalSite }
29. static var settings: Page { return Page.settings } static func externalSite(_ url: URL) -> Page { return Page.externalSite(url) } let _: (URL) -> Page = Page.externalSite enum Page { case settings case externalSite(URL) }
30. [1.1, 3.2 ,3.5].map(round) [1.1, 3.2 ,3.5].sorted(by: <) ["www.ezura.me", ""].flatMap(URL.init)
31. inout
32. let _: (Int...) -> String = f let _: (Int) -> String = SomeType().f let _: (SomeType) -> (Int) -> String = SomeType.f let _: (Int, Int) -> (Int) = (+) let _: (inout Int, Int) -> () = (+=) let _: (URL) -> Page = Page.externalSite inout
33. static func +=(lhs: inout Self, rhs: Self) var x = 1 // x: 1 x += 1 // x: 2 inout
34. ! error: Escaping closures can only capture
 inout parameters explicitly by value func f(_ arg: inout String) -> () -> () { return { print(arg) } }
35. func f(_ arg: inout String) { arg = "" arg = "" } var testString = "" { didSet { print("changed: \(testString)") } } f(&testString) changed:
36. change to “" change to “" func f(_ arg: inout String) var testString "" "" "" "" ""
37. current testString: changed: func f(_ arg: inout String) { arg = "" sleep(2) arg = "" } var testString = "" { didSet { print("changed: \(testString)") } } DispatchQueue.global().asyncAfter(deadline: .now() + .seconds(1)) { print("current testString: \(testString)") } f(&testString)
38. func f(_ arg: inout String) { arg = "" sleep(2) arg = "" } var testString = "" /* { didSet { print("changed: \(testString)") } } */ DispatchQueue.global().asyncAfter(deadline: .now() + .seconds(1)) { print("current testString: \(testString)") } f(&testString) current testString:
39. change to “" change to “" func f(_ arg: inout String) var testString "" "" ""
40. func f(_ arg: inout String) inout change to “" change to “" var testString "" "" "" "" "" ""
41. inout return defer
42. defer execute after all other code in the scope
43. x++, ++x or neither? /* ??? */ func ++(x: inout Int) -> Int { defer { x += 1 } return x }
44. postfix func ++(x: inout Int) -> Int { defer { x += 1 } return x } x++
45. func f() { let v: String defer { print(v) } v = "init value" }
46. func f() { let v: String defer { print(v) } v = "init value" }
47. class SomeType { var v: String { didSet { … } } init() { defer { v = " in defer" } v = "" v = "" } }
48. deinit { defer { v = "goodbye in defer" } changeV() _ = { v = "goodbye in block" }() }
49. Swift Tour = (obj?.myVariable = 50) .map { /* … */ } { while(true) {} }() let _: (inout Int, Int) -> () = (+=) let _: (URL) -> Enum = Enum.case Closure
50. inout func f(_ arg: inout String) -> () -> () { return { print(arg) } } copy-in copy-out / Optimized inout defer return
51. defer init() { defer { v = " in defer" } v = " initialize" } deinit { v = "goodbye " defer { v = "goodbye in defer" } }
52. Swift Tour myVariable = 50 obj?.myVariable = 50 return Closure defer didSet inout enum Never init, deinit
53. Thank you for listening!!