How does defining [square bracket] method in Ruby work?

Question

I am going through Programming Ruby - a pragmatic programmers guide and have stumbled on this piece of code:

class SongList
  def [](key)
    if key.kind_of?         


        

Answer 1

the square brackets are the method name like Array#size you have Array#[] as a method and you can even use it like any other method:

array = [ 'a', 'b', 'c']
array.[](0) #=> 'a'
array.[] 1  #=> 'b'
array[2]    #=> 'c'

the last one is something like syntactic sugar and does exactly the same as the first one. The Array#+ work similar:

array1 = [ 'a', 'b' ]
array2 = [ 'c', 'd' ]
array1.+(array2) #=> [ 'a', 'b', 'c', 'd' ]
array1.+ array2  #=> [ 'a', 'b', 'c', 'd' ]
array1 + array2  #=> [ 'a', 'b', 'c', 'd' ]

You can even add numbers like this:

1.+(1) #=> 2
1.+ 1  #=> 2
1 + 1  #=> 2

the same works with /, *, - and many more.