Mixins

ruby-talk
1

Hi guys!!!
My question is:

  Is any way to define variables in module which can be further used in
mixin? The problem is that module I wanted to include into class has
constant variables defined which are used within function it implements.
I'm looking for simplest way to overwrite the variables from the class
(may change the variables to non constant ones) the same meaning not to
change implementation of functions from the module. See:

module Mod
AnyVar = 10

def func
   #the method use AnyVar
end
end

class MyClass
include Mod

def initialize
  #read configuration

  #how to make the function use new AnyVar value without changing its
implementation and parameters list
  func()
end
end

Thanks a lot for any ideas.

···

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2

I don't know if I get the point but this seems work:

module Mod
@anyvar = 10

def func
  puts @anyvar
end
end

class MyClass
include Mod

def initialize
#read configuration
@anyvar = 2
func()
end

end

MyClass.new
# => 2

···

On Tue, Apr 29, 2008 at 10:01 AM, Marcin Tyman <m.tyman@interia.pl> wrote:

Hi guys!!!
My question is:

  Is any way to define variables in module which can be further used in
mixin? The problem is that module I wanted to include into class has
constant variables defined which are used within function it implements.
I'm looking for simplest way to overwrite the variables from the class
(may change the variables to non constant ones) the same meaning not to
change implementation of functions from the module. See:

module Mod
  AnyVar = 10

  def func
   #the method use AnyVar
  end
end

class MyClass
  include Mod

  def initialize
  #read configuration

  #how to make the function use new AnyVar value without changing its
implementation and parameters list
  func()
  end
end

Thanks a lot for any ideas.
--
Posted via http://www.ruby-forum.com/\.

--
Go outside! The graphics are amazing!

3

Marcin Tyman wrote:

Hi guys!!!
My question is:

  Is any way to define variables in module which can be further used in
mixin? The problem is that module I wanted to include into class has
constant variables defined which are used within function it implements.
I'm looking for simplest way to overwrite the variables from the class
(may change the variables to non constant ones) the same meaning not to
change implementation of functions from the module. See:

module Mod
AnyVar = 10

def func
   #the method use AnyVar
end
end

class MyClass
include Mod

def initialize
  #read configuration

  #how to make the function use new AnyVar value without changing its
implementation and parameters list
  func()
end
end

Thanks a lot for any ideas.
  
I am not sure I quite understand what you are trying to do, but you can do something like this:

module A
        def initialize
                super
                @var = 1
        end
end

class B
        include A

        def initialize
                super
        end

        def check_var
                puts @var
        end
end

B.new.check_var #=> 1

The trouble is you need to make sure you call 'super' religiously if you are including a lot of modules.

-Justin

4

Yep, you're my hero :wink: Works well.

···

--
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5

Hi --

I don't know if I get the point but this seems work:

module Mod
@anyvar = 10

def func
puts @anyvar
end

You've got two variables called @anyvar in that code, and they have no
relation to each other.

The first one is an instance variable belonging to the module Mod
(that is, the actual object Mod). The second one represents an
instance variable that will belong to each object that executes the
func method.

So the @anyvar = 10 line is serving no purpose.

David

···

On Tue, 29 Apr 2008, Sandro Paganotti wrote:

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6

Well, maybe you can try this way...

module Mod

def Mod.included(mod)
mod.class_eval <<-EOS
    alias_method :old_initialize, :initialize
    def initialize
      @anyvar = 10
      old_initialize
    end
EOS
end

def func
puts @anyvar
end
end

class MyClass

  def initialize
  #read configuration
  puts @anyvar
  @anyvar = 2
  func()
  end

include Mod
end

MyClass.new
# => 10
# => 2

···

On Tue, Apr 29, 2008 at 11:03 AM, David A. Black <dblack@rubypal.com> wrote:

Hi --

On Tue, 29 Apr 2008, Sandro Paganotti wrote:

> I don't know if I get the point but this seems work:
>
> module Mod
> @anyvar = 10
>
> def func
> puts @anyvar
> end
> end
>

You've got two variables called @anyvar in that code, and they have no
relation to each other.

The first one is an instance variable belonging to the module Mod
(that is, the actual object Mod). The second one represents an
instance variable that will belong to each object that executes the
func method.

So the @anyvar = 10 line is serving no purpose.

David

--
Rails training from David A. Black and Ruby Power and Light:
  INTRO TO RAILS June 9-12 Berlin
  ADVANCING WITH RAILS June 16-19 Berlin
  INTRO TO RAILS June 24-27 London (Skills Matter)
See http://www.rubypal.com for details and updates!

--
Go outside! The graphics are amazing!