Synopsys

Enumerable#filter - extended Enumerable#select

Examples

String filter (acts like Enumerable#grep):

[1, 2, 3, 'ab'].filter(/a/)              # => #<Enumerator: ['ab']>
[1, 2, 3, '3'].filter('3')               # => #<Enumerator: ['3']>

You can pass a Proc or Symbol. Methods and blocks are allowed too:

[1, 2, 3].filter(&:even?)                # => #<Enumerator: [2]>
[1, 2, 3].filter(:even?)                 # => #<Enumerator: [2]>
[1, 2, 4].filter { |num| num.even? }     # => #<Enumerator: [2, 4]>

Enumerable#filter can match against enumerable items attributes. Like this:

[1, 2, 3, 4.2].filter :to_i => :even?    # => #<Enumerator: [2, 4]>

If the block is supplied, each matching element is passed to it, and the block’s result is stored in the output enumerator.

[1, 2, 4].filter(&:even?) { |n| n + 1 }  # => #<Enumerator: [3, 5]>

Enumerable#filter also accepts true or false as argument:

[0, false, 2, nil].filter(true)          # => #<Enumerator: [0, 2]>
[0, false, 2, nil].filter(false)         # => #<Enumerator: [false, nil]>