Duck typing and core idioms
| If it quacks | |
| To_s and inspect | |
| Comparable and sorting | |
| Freeze constants |
If it quacks
Duck typing means Ruby cares about methods, not class names. If an object responds to quack, the caller treats it as a duck.
This keeps code flexible: new classes work with old methods without any shared parent. Collections of such objects are easy to process with
Enumerables.
def greet(thing)
puts "Hello, " + thing.to_s
end
greet("Ada")
greet(42)
To_s and inspect
to_s gives the friendly reading form: the text you show to users. inspect gives the programmer form with extra marks like quotes.
puts calls to_s, while p calls inspect. During debugging, p shows you the real structure.
n = 42
puts n.to_s
p n
Comparable and sorting
Include Comparable and define <=> to gain sorting and all six comparison checks from one definition.
The method returns minus one, zero, or plus one depending on order. sort uses it automatically.
class Size
include Comparable
attr_reader :cm
def initialize(cm)
@cm = cm
end
def <=>(other)
@cm <=> other.cm
end
end
puts Size.new(3) < Size.new(9)
Freeze constants
Constants can still change inside when they point to arrays or strings. Freeze them so accidental edits raise an error instead of corrupting state.
Capitalized names warn on reassignment but do not lock the object. Only freeze locks the content.
COLORS = ["red", "blue"].freeze
APP = "aredel".freeze
Next: Gems and Bundler
Article author: Arthur Isaev