Ruby by Example

#21 Using Procs for Filtering (matching_members.rb)

So far, we’ve seen that to create a Proc, we call lambda with a block describing what that Proc should do. This would lead you to believe that there is a special relationship between Procs and blocks, which there is. Our next script demonstrates how to use Procs in place of blocks.

The Code

  #!/usr/bin/env ruby
  # matching_members.rb

  =begin rdoc
  Extend the built-in <b>Array</b> class.
  =end
  class Array

  =begin rdoc
  Takes a <b>Proc</b> as an argument, and returns all members
  matching the criteria defined by that <b>Proc</b>.
  =end
❶   def matching_members(some_proc)    Procs as Arguments find_all { |i| some_proc.call(i) } end end ❷ digits = (0..9).to_a lambdas = Hash.new() lambdas['five+'] = lambda { |i| ...