Confusion with Forwarrordable#delegate - throwing an er

ruby-talk
1

require 'forwardable'

class MyQueue

  extend Forwardable
  attr_reader :queue

  def initialize
    @queue = []
  end

  def_delegator :@queue, :push, :mypush

end

q = MyQueue.new

q.instance_delegate [:clear, :first] => @q
#`<main>': undefined method `instance_delegate' for #<MyQueue:0x2119e48
@queue=[]> (NoMethodError)

q.delegate [:clear, :first] => @q

#`<main>': undefined method `delegate' for #<MyQueue:0x2109e40
@queue=[]> (NoMethodError)

Can you tell me what wrong I did? How to fix that?

···

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2

Can anyone help me in this post?

Thanks

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3

What are you trying to do exactly? If you want to add a couple of delegations to an instance of MyQueue then maybe this is what you want to do:

# ... your class definition

def exercise(obj)
  puts "exercising #{obj}"
  puts obj.first
  obj.mypush 'foo'
  puts obj.first
  obj.clear
  puts obj.first
end

q1 = MyQueue.new
class << q1
  delegate [:clear, :first] => :@queue
end

q2 = MyQueue.new
exercise q1 # should have first & clear methods delegated
exercise q2 # should complain at the first call of first

Hope this helps,

Mike

···

On 2013-04-07, at 2:50 AM, Love U Ruby <lists@ruby-forum.com> wrote:

require 'forwardable'

class MyQueue

extend Forwardable
attr_reader :queue

def initialize
   @queue = []
end

def_delegator :@queue, :push, :mypush

end

q = MyQueue.new

q.instance_delegate [:clear, :first] => @q
#`<main>': undefined method `instance_delegate' for #<MyQueue:0x2119e48
@queue=[]> (NoMethodError)

q.delegate [:clear, :first] => @q

#`<main>': undefined method `delegate' for #<MyQueue:0x2109e40
@queue=[]> (NoMethodError)

Can you tell me what wrong I did? How to fix that?

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--

Mike Stok <mike@stok.ca>
http://www.stok.ca/~mike/

The "`Stok' disclaimers" apply.

4

Mike Stok wrote in post #1105046:

q1 = MyQueue.new
class << q1
  delegate [:clear, :first] => :@queue
end

Okay! So you defined it in the singleton class of `q1`. Why we need to
define it in the singleton class? BTW who is the caller of the method
`delegate`?

Thanks

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