Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Types and Refactoring
Search
Penelope Phippen
July 21, 2014
Technology
3
190
Types and Refactoring
A talk about types and refactoring I gave at Brighton Ruby 2014.
Penelope Phippen
July 21, 2014
Tweet
Share
More Decks by Penelope Phippen
See All by Penelope Phippen
Introducing Rubyfmt
penelope_zone
0
560
How RSpec Works
penelope_zone
0
6.6k
Quick and easy browser testing using RSpec and Rails 5.1
penelope_zone
1
82
Teaching RSpec to play nice with Rails
penelope_zone
2
140
Little machines that eat strings
penelope_zone
1
99
What is processor (brighton ruby edition)
penelope_zone
0
110
What is processor?
penelope_zone
1
350
extremely defensive coding - rubyconf edition
penelope_zone
0
260
Agile, etc.
penelope_zone
2
220
Other Decks in Technology
See All in Technology
Zero Data Loss Autonomous Recovery Service サービス概要
oracle4engineer
PRO
2
7.8k
TLSから見るSREの未来
atpons
2
240
〜『世界中の家族のこころのインフラ』を目指して”次の10年”へ〜 SREが導いたグローバルサービスの信頼性向上戦略とその舞台裏 / Towards the Next Decade: Enhancing Global Service Reliability
kohbis
3
1.1k
american aa airlines®️ USA Contact Numbers: Complete 2025 Support Guide
aaguide
0
500
20250707-AI活用の個人差を埋めるチームづくり
shnjtk
6
4.1k
SREの次のキャリアの道しるべ 〜SREがマネジメントレイヤーに挑戦して、 気づいたこととTips〜
coconala_engineer
1
1k
DBのスキルで生き残る技術 - AI時代におけるテーブル設計の勘所
soudai
PRO
55
22k
united airlines ™®️ USA Contact Numbers: Complete 2025 Support Guide
flyunitedhelp
1
470
事例で学ぶ!B2B SaaSにおけるSREの実践例/SRE for B2B SaaS: A Real-World Case Study
bitkey
1
340
モニタリング統一への道のり - 分散モニタリングツール統合のためのオブザーバビリティプロジェクト
niftycorp
PRO
1
360
QuickSight SPICE の効果的な運用戦略~S3 + Athena 構成での実践ノウハウ~/quicksight-spice-s3-athena-best-practices
emiki
0
260
IPA&AWSダブル全冠が明かす、人生を変えた勉強法のすべて
iwamot
PRO
2
220
Featured
See All Featured
Optimising Largest Contentful Paint
csswizardry
37
3.3k
GitHub's CSS Performance
jonrohan
1031
460k
Java REST API Framework Comparison - PWX 2021
mraible
31
8.7k
Improving Core Web Vitals using Speculation Rules API
sergeychernyshev
18
980
Principles of Awesome APIs and How to Build Them.
keavy
126
17k
We Have a Design System, Now What?
morganepeng
53
7.7k
Embracing the Ebb and Flow
colly
86
4.7k
Producing Creativity
orderedlist
PRO
346
40k
Navigating Team Friction
lara
187
15k
Put a Button on it: Removing Barriers to Going Fast.
kastner
60
3.9k
The Cost Of JavaScript in 2023
addyosmani
51
8.5k
Creating an realtime collaboration tool: Agile Flush - .NET Oxford
marcduiker
30
2.1k
Transcript
Types & Refactoring
a!/samphippen
Types
I think type systems are great!
I think dynamic languages are great!
I think thinking about types in dynamic languages is great!
RUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUUUUUUUUUUUUUU UUUUUUUUUUUUUBYYYYYYYYYYYYYY YYYYYYYYYYYYYYYYYYYYYYYYYYYYYY YYYYYYYYYYYYYYYYYYYYYYYYYYYYYY YYYYYYYYYYYYYYYYYYYYYYYYYYYYYY
No type systems here
NoMethodError: undefined method `foo' for nil:NilClass
No explicit type systems here
What is a type?
Concrete implementation of some data and behaviour
Class
1.class # => FixNum
(1.0).class # => Float
What is a typeclass?
A set of methods satisfied by many types
Interface
(1+1.0).class # => Float (1.0+1).class # => Float
But also things like
Positive Int + Positive Int # => Positive Int
some_collection.count
String Hash Array
Form a typeclass (or interface) under count with no args
Methods that return consistent interfaces are great
The problem
We’re not forced to return a single interface
If interface is inconsistent, code must check types further down
For example returning nil
nil is not type classed the same as your object!
pony = Pony.find_by(:key => value) if pony pony.neigh else puts
“pony was nil” end
The if is a subtle form of type checking.
Type checking is the antithesis of OO
Can we get a consistent interface?
Refactoring
Null object
class Pony def horse_power 0.5 end end
Pony.find_by( :key => value ) || NullPony.new
class NullPony def horse_power 0 end end
Decides default for horse_power at define time
May or may not be what you want
Maybe
Steal ideas from functional programming!
Decide defaults at run time
Maybe is a type class
#map(&blk) -> maybe #value_or(x) -> Object
class Just def initialize(value) @value = value end def map(&blk)
def value_or(x) Just.new(blk.call(@value)) @value end end end
class Nothing def map(&blk) self end def value_or(x) x end
end
Map until done with transforms
use maybe.value_or(“something”)
Recap
Methods that return nil are almost always inconsistently typed
Use a null object to replace a nil if you
know defaults at define time
Use maybe if you want to set defaults at run
time
RSpec RSpec ! ! RSpec 3
tinyurl.com/ sambr2014
Let’s have some questions a!/samphippen
[email protected]