Class: SimpleDelegator

Inherits:
Delegator show all
Defined in:
opal/stdlib/delegate.rb

Overview

A concrete implementation of Delegator, this class provides the means to delegate all supported method calls to the object passed into the constructor and even to change the object being delegated to at a later time with

setobj.

class User def born_on Date.new(1989, 9, 10) end end

require 'delegate'

class UserDecorator < SimpleDelegator def birth_year born_on.year end end

decorated_user = UserDecorator.new(User.new) decorated_user.birth_year #=> 1989 decorated_user.getobj #=> #

A SimpleDelegator instance can take advantage of the fact that SimpleDelegator is a subclass of +Delegator+ to call super to have methods called on the object being delegated to.

class SuperArray < SimpleDelegator def super + 1 end end

SuperArray.new([1])[0] #=> 2

Here's a simple example that takes advantage of the fact that SimpleDelegator's delegation object can be changed at any time.

class Stats def initialize @source = SimpleDelegator.new([]) end

def stats(records)
  @source.__setobj__(records)

  "Elements:  #{@source.size}\n" +
  " Non-Nil:  #{@source.compact.size}\n" +
  "  Unique:  #{@source.uniq.size}\n"
end

end

s = Stats.new puts s.stats(%wEdward Gray II) puts puts s.stats([1, 2, 3, nil, 4, 5, 1, 2])

Prints:

Elements: 4 Non-Nil: 4 Unique: 4

Elements: 8 Non-Nil: 7 Unique: 6

Constant Summary

Constants inherited from Delegator

Delegator::VERSION

Instance Method Summary collapse

Methods inherited from Delegator

#!, #!=, #==, const_missing, delegating_block, #eql?, #freeze, #frozen?, #initialize, #marshal_dump, #marshal_load, #methods, #protected_methods, public_api, #public_methods, #respond_to_missing?

Constructor Details

This class inherits a constructor from Delegator

Instance Method Details

#__getobj__ ⇒ Object

Returns the current object method calls are being delegated to.



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# File 'opal/stdlib/delegate.rb', line 332

def __getobj__
  unless defined?(@delegate_sd_obj)
    return yield if block_given?
    __raise__ ::ArgumentError, 'not delegated'
  end
  @delegate_sd_obj
end

#__setobj__(obj) ⇒ Object

Changes the delegate object to obj.

It's important to note that this does not cause SimpleDelegator's methods to change. Because of this, you probably only want to change delegation to objects of the same type as the original delegate.

Here's an example of changing the delegation object.

names = SimpleDelegator.new(%wEdward Gray II) puts names[1] # => Edward names.setobj(%wSinclair) puts names[1] # => Sinclair



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# File 'opal/stdlib/delegate.rb', line 354

def __setobj__(obj)
  __raise__ ::ArgumentError, 'cannot delegate to self' if equal?(obj)
  @delegate_sd_obj = obj
end