Rubyのメソッド引数

ちょっと調べたので書いとく

% ruby -v
ruby 2.0.0p481 (2014-05-08 revision 45883) [universal.x86_64-darwin14]

普通

class Sample
  def hoge
    p "hoge"
  end
end

sample = Sample.new
sample.hoge

"hoge"

引数のデフォルト

class Sample
  def hoge(a, b=1)
    p "a:#{a}, b:#{b}"
  end
end

sample = Sample.new
sample.hoge(1, 2)
sample.hoge(1)
sample.hoge

"a:1, b:2"
"a:1, b:1"
`hoge': wrong number of arguments (0 for 1..2) (ArgumentError)

可変長引数

class Sample
  def hoge(*args)
    p args.join(",")
  end
end

sample = Sample.new
sample.hoge
sample.hoge(1, "hoge", {a: 100})

""
"1,hoge,{:a=>100}"

キーワード引数

class Sample
  def hoge(a: "aaa", b: "bbb")
    p "a:#{a}, b:#{b}"
  end
end

sample = Sample.new
sample.hoge
sample.hoge(a: "1", b: "2")
sample.hoge(b: "1", a: "2")
sample.hoge(b: "100")

a:aaa, b:bbb"
"a:1, b:2"
"a:2, b:1"
"a:aaa, b:100"

同名メソッド

class Sample
  def hoge
    p "hoge"
  end

  def hoge(i)
    p "hoge #{i}"
  end
end

ample = Sample.new
sample.hoge
sample.hoge(5)

`hoge': wrong number of arguments (0 for 1) (ArgumentError)