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
540
How RSpec Works
penelope_zone
0
6.5k
Quick and easy browser testing using RSpec and Rails 5.1
penelope_zone
1
77
Teaching RSpec to play nice with Rails
penelope_zone
2
120
Little machines that eat strings
penelope_zone
1
84
What is processor (brighton ruby edition)
penelope_zone
0
95
What is processor?
penelope_zone
1
340
extremely defensive coding - rubyconf edition
penelope_zone
0
250
Agile, etc.
penelope_zone
2
210
Other Decks in Technology
See All in Technology
AI自体のOps 〜LLMアプリの運用、AWSサービスとOSSの使い分け〜
minorun365
PRO
9
750
エンジニアリング価値を黒字化する バリューベース戦略を用いた 技術戦略策定の道のり
kzkmaeda
7
3.2k
JavaにおけるNull非許容性
skrb
2
2.7k
"TEAM"を導入したら最高のエンジニア"Team"を実現できた / Deploying "TEAM" and Building the Best Engineering "Team"
yuj1osm
1
230
Qiita Organizationを導入したら、アウトプッターが爆増して会社がちょっと有名になった件
minorun365
PRO
1
200
DevinでAI AWSエンジニア製造計画 序章 〜CDKを添えて〜/devin-load-to-aws-engineer
tomoki10
0
190
Amazon Aurora のバージョンアップ手法について
smt7174
2
180
入門 PEAK Threat Hunting @SECCON
odorusatoshi
0
170
AWS Well-Architected Frameworkで学ぶAmazon ECSのセキュリティ対策
umekou
2
150
わたしがEMとして入社した「最初の100日」の過ごし方 / EMConfJp2025
daiksy
14
5.3k
データエンジニアリング領域におけるDuckDBのユースケース
chanyou0311
9
2.5k
4th place solution Eedi - Mining Misconceptions in Mathematics
rist
0
150
Featured
See All Featured
A Modern Web Designer's Workflow
chriscoyier
693
190k
GraphQLの誤解/rethinking-graphql
sonatard
69
10k
Cheating the UX When There Is Nothing More to Optimize - PixelPioneers
stephaniewalter
280
13k
Done Done
chrislema
182
16k
Optimizing for Happiness
mojombo
377
70k
Being A Developer After 40
akosma
89
590k
Documentation Writing (for coders)
carmenintech
68
4.6k
Templates, Plugins, & Blocks: Oh My! Creating the theme that thinks of everything
marktimemedia
30
2.2k
Stop Working from a Prison Cell
hatefulcrawdad
268
20k
ReactJS: Keep Simple. Everything can be a component!
pedronauck
666
120k
Measuring & Analyzing Core Web Vitals
bluesmoon
6
260
Designing on Purpose - Digital PM Summit 2013
jponch
117
7.1k
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]