I have some difficulties for using Ruby block, passing in a method.
As in the following case, I would like to display each element of @array, from Box instance (using .each method):
class Box
def initialize
@array = [:foo, :bar]
end
def each(&block)
# well, hm..
end
end
a = Box.new
a.each { |element| puts element }
You really just need to delegate to the each method on @array and pass it the block. Additionally, you can include the Enumerable mix-in to gain access to the methods it provides (e.g. map, inject, etc...):
class Box
include Enumerable
def initialize
@array = [:foo, :bar]
end
def each(&block)
@array.each(&block)
end
end
More information on the Enumerable module is available in the documentation.
require 'forwardable', and then inside Box: extend Forwardable and def_delegator(:@array, :each)For this simple example, you actually aren't required to pass the block explicitly:
def each
@array.each{|e| yield e}
end
Passing the block (which is a Proc object) explicitly allows you to test it for things, like the number of arguments that it expects:
class Box
...
def each(&block)
@array.each do |e|
case block.arity
when 0
yield
when 1
yield e
when 2
yield e, :baz
else
yield
end
end
end
end
a = Box.new
a.each { puts "nothing" } # displays "nothing, nothing"
a.each { |e| puts e } # displays "foo, bar"
a.each { |e1, e2| puts "#{e1} #{e2}" } # displays "foo baz, bar baz"
