Module_eval: create method that contains value passed to it?

ruby-talk
1

This is a Rails example, but I think the problem is a general Ruby
matter.

I am using class_eval within a class method, foobar(), to have it create
an instance method, get_foobar(). I am passing a value ("testing testing
123") to foobar() that I want to make part of get_foobar(). However, I
can't seem to include this value in the output of get_foobar().

Where I want the "render" line to output "A start testing testing 123
end O", it only outputs "A start end O". Extremely grateful for any
help. Code:

  class HelpController < ApplicationController

    def self.foobar(v)

      class_eval %q{
        def get_foobar()
          "start #{v} end"
        end
      }

    end

    foobar "testing testing 123"

     def index
      render :text => "A "+get_foobar+" O"
    end

  end

Or syntax highlighted here: http://rafb.net/paste/results/igothN18.html

···

--
Posted via http://www.ruby-forum.com/.

2

Henrik wrote:

This is a Rails example, but I think the problem is a general Ruby matter.

Perhaps, but it would be more helpful to isolate the problem by removing all Rails influence, since there is every chance that Rails is munging up core Ruby behavior.

But I think the problem is simply that you are not quoting your strings correctly:

   class HelpController
    def self.foobar(v)
      class_eval %Q{
        def get_foobar()
          "start #{v} end"
        end
      }
    end

    foobar "testing testing 123"
     def index
      puts "A " + get_foobar + " O"
    end
  end

   HelpController.new.index # A start testing testing 123 end O

(Big Q, not little q)

I have no idea if this works on the railroad.

James

···

--

http://www.ruby-doc.org - Ruby Help & Documentation
Ruby Code & Style - Ruby Code & Style: Writers wanted
http://www.rubystuff.com - The Ruby Store for Ruby Stuff
http://www.jamesbritt.com - Playing with Better Toys
http://www.30secondrule.com - Building Better Tools

3

This is a Rails example, but I think the problem is a general Ruby
matter.

I am using class_eval within a class method, foobar(), to have it
create an instance method, get_foobar(). I am passing a value
("testing testing 123") to foobar() that I want to make part of
get_foobar(). However, I can't seem to include this value in the
output of get_foobar().

Where I want the "render" line to output "A start testing testing 123
end O", it only outputs "A start end O". Extremely grateful for any
help. Code:

class HelpController < ApplicationController

  def self.foobar(v)

    class_eval %q{
      def get_foobar()
        "start #{v} end"
      end
    }

  end

  foobar "testing testing 123"

   def index
    render :text => "A "+get_foobar+" O"
  end

end

Or syntax highlighted here:
http://rafb.net/paste/results/igothN18.html

You don't even need class_eval - a simple closure is sufficient:

class X
  def self.foobar(x)
    define_method(:get_foobar) { x }
  end
    foobar "testing testing 123"
end

x=X.new

=> #<X:0x101c1198>

x.get_foobar

=> "testing testing 123"

X.foobar "qwert"

=> #<Proc:0x101c8530@(irb):3>

x.get_foobar

=> "qwert"

Kind regards

    robert

···

Henrik <henrik@nyh.se> wrote:

4

this can be done with closures or a storage/search-path scheme. the traits
lib uses the latter, see here:

   Index of /lib/ruby/traits

-a

···

On Sun, 8 Jan 2006, Henrik wrote:

This is a Rails example, but I think the problem is a general Ruby
matter.

I am using class_eval within a class method, foobar(), to have it create
an instance method, get_foobar(). I am passing a value ("testing testing
123") to foobar() that I want to make part of get_foobar(). However, I
can't seem to include this value in the output of get_foobar().

Where I want the "render" line to output "A start testing testing 123
end O", it only outputs "A start end O". Extremely grateful for any
help. Code:

  class HelpController < ApplicationController

    def self.foobar(v)

      class_eval %q{
        def get_foobar()
          "start #{v} end"
        end
      }

    end

    foobar "testing testing 123"

     def index
      render :text => "A "+get_foobar+" O"
    end

  end

Or syntax highlighted here: http://rafb.net/paste/results/igothN18.html

--
Posted via http://www.ruby-forum.com/\.

--

ara [dot] t [dot] howard [at] noaa [dot] gov
strong and healthy,
who thinks of sickness until it strikes like lightning?
preoccupied with the world,
who thinks of death, until it arrives like thunder?
-- milarepa

===============================================================================