Iterators

class Trio include Enumerable def initialize(a, b, c) @items = [a, b, c] end def each @items.each { |item| yield item } end end t = Trio.new('x', 'y', 'z') t.each { |item| puts item } p t.collect { |item| item.upcase } p t.select { |item| item =~ /[xz]/ } p t.reject { |item| item =~ /[xz]/ } p t.find { |item| item =~ /[yz]/ } p t.inject('') { |item, sum| sum + item } p t.grep(/[z]/)

Output

x y z ["X", "Y", "Z"] ["x", "z"] ["y"] "y" "zyx" ["z"]

All containers in Ruby implement an each that yields a block to each item in the container.

The Enumerable module mixin implements a number of methods in terms of each.
- collect returns a new list with yielded values
- select returns a new list containing a subset of the original that passes the yielded test
- reject like select, but inverts the meaning of the test.

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