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Rubyのeachメソッドで繰り返し回数を指定する方法

Last updated at Posted at 2019-01-10

やりたい処理

eachメソッドで配列を繰り返し処理する際に、回数を指定したい。

通常

countries = ["Japan", "America", "China", "Korea", "Canada", "Brazil", "Bhutan"]
countries.each do |country|
  puts country
end
#  Japan America China Korea Canada Brazil Bhutan

first(回数)

回数を指定する場合firstメソッドを使用し、引数に回数を指定する。

countries = ["Japan", "America", "China", "Korea", "Canada", "Brazil", "Bhutan"]
countries.first(3).each do |country|
  puts country
end
#  Japan America China

ちなみ同時にshuffleメソッドを使うとランダムに指定した回数分取り出せる。

countries = ["Japan", "America", "China", "Korea", "Canada", "Brazil", "Bhutan"]
countries.shuffle.first(3).each do |country|
  puts country
end
#  ランダムで3つ

参考

https://ref.xaio.jp/ruby/classes/array/first
https://ref.xaio.jp/ruby/classes/array/shuffle

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