String#[]
sliceのエイリアスメソッド
好きなメソッド
code:ruby
irb(main):059:0> a = 'abcde'
=> "abcde"
irb(main):060:0> ary = a.split('')
irb(main):061:0> ary2 = 'C' => "C"
irb(main):062:0> ary.join
=> "abCde"
[]を使えば一発で変更できる
code:ruby
irb(main):066:0> a = 'abcde'
=> "abcde"
irb(main):067:0> a2 = 'C' => "C"
irb(main):068:0> a
=> "abCde"