Add dynamic instance methods in a controller

Rails
1

Hello All,

I have a problem while developping an application using rails.
I’d like to add some methods to my controller depending upon some
parameters read from an xml file during initialisation (I hope I am
quite clear :slight_smile: )
Below is the code I am using:

require ‘rexml/Document’
include REXML

class MyController < ApplicationController

   def index
           # Xsd is a model (not ActiveRecord that is used to get

values from an XML file
xsd = Xsd.new(“myfile.xsd”)

           # Get main section
           @main_sections = xsd.get_main_sections

           # Get item for first section
           @item =

xsd.get_items_per_section(@main_sections[0].to_s)

           # Dynamically create method for to retrieve list of

fields for each
main sections
# THIS PART IS NOT WORKING
@main_sections.each do |section|
self.instance_eval{
define_method(“get_item_for_#{section}”) {“toto”}}
end
end
end

While testing this, I have an error message saying that the
define_method does not exist !!!
Why is this method not found ???
I am still not sure about the instance_eval, class_eval, define_method
I need to use.
Do you have any clues regarding this problem ?

Thanks a lot,

Luc

2

Hi Luc,

I am facing the same problem loading the data from YAML and using AR to
store metrics only and final data.

I am still looking for a solution to dynamically create attributes but i
am not that the controller is the place to do that. I believe it should
be done on the model level.

Did you think about the possibility of creating a class and load the
methods into it?

Try this link to learn more about metaprogramming:

Cheers,

Luc wrote:

Hello All,

I have a problem while developping an application using rails.
I’d like to add some methods to my controller depending upon some
parameters read from an xml file during initialisation (I hope I am
quite clear :slight_smile: )
Below is the code I am using:

require ‘rexml/Document’
include REXML

class MyController < ApplicationController

   def index
           # Xsd is a model (not ActiveRecord that is used to get

values from an XML file
xsd = Xsd.new(“myfile.xsd”)

           # Get main section
           @main_sections = xsd.get_main_sections

           # Get item for first section
           @item =

xsd.get_items_per_section(@main_sections[0].to_s)

           # Dynamically create method for to retrieve list of

fields for each
main sections
# THIS PART IS NOT WORKING
@main_sections.each do |section|
self.instance_eval{
define_method(“get_item_for_#{section}”) {“toto”}}
end
end
end

While testing this, I have an error message saying that the
define_method does not exist !!!
Why is this method not found ???
I am still not sure about the instance_eval, class_eval, define_method
I need to use.
Do you have any clues regarding this problem ?

Thanks a lot,

Luc