Class_eval method scope

rubyonrails-talk
1

class AssigneesController < ApplicationController

def assignees

Assignee.class_eval %Q{

def assignee_name

self[“#{params[:assignee_by]}”]

end

}

end

def do_assignee_cleaning

Assignee.assignee_name

redirect_to assignee_cleaning_project_assignees_path(params[:project_id])

end

end

I want to use assignee_name method in do_assignee_cleaning action but i am getting error undefined

method assignee_name' for class Assignee’ in do_assignee_cleaning

2

In an effort to understand the question (not having used class_eval) I found the following link that suggests, rather non-intuitively, that you should be using instance_eval rather than class_eval.

http://ilikestuffblog.com/2009/01/09/fun-with-rubys-instance_eval-and-class_eval/

Colin

3

sorry for mistake not Assignee.assignee_name

Assignee.find(1).assignee_name

4

sorry for mistake not Assignee.assignee_name Assignee.find(1).assignee_name

Do you mean that you have fixed the problem by that change, or that you had a mistake in the question you asked and with Assignee.find(1).assignee_name it still fails?

Colin

5

yes still fails Assignee.find(1).assignee_name

6

yes still fails Assignee.find(1).assignee_name

Please don't top post, it makes it difficult to follow the thread. Insert your reply at appropriate points in previous message. Thanks.

Can you post the full error message and the stack trace please along with the exact code (copy/paste rather than re-type).

Colin

7

yes still fails Assignee.find(1).assignee_name

I presume that you *have* called assignees before calling do_assignee_cleaning.

Colin

8

Curious why you would want to define the method that way, are you overriding the method assignee_name which is already defined in the Assignee class?

If not, then why not define it directly in the model like this:

def assignee_name(assigned_by)

self[“assigned_by”]

end

Controller method will be

def do_assignee_cleaning

Assignee.assignee_name(params[:assignee_by])

redirect_to assignee_cleaning_project_assignees_path(params[:project_id])

end

9

Thanks for your reply

I thought class_eval method would permanently add assignee_name method to Assignee instance object and i can access from other action too.

10

Thanks for your reply

Please don't top post, it makes it difficult to follow the thread. Insert your reply at appropriate points in previous message. Thanks.

I thought class_eval method would permanently add assignee_name method to Assignee instance object and i can access from other action too.

I think it will, but only when you execute the class_eval code. Permanent means of course until you restart the server or reload the Assignee class. Since in development mode classes are reloaded at each action request it will not hold from one request to the next, if that is what you are trying to do. Even in production this is a bad thing to do as you never know when a server might get restarted and loose the data. Not to mention the fact that once in production successive actions are not necessarily even run by the same computer. If you want retain information from one action to the next then put it in the session or in the database, or in a hidden field in the intervening view.

I think Chirag Singhal's suggestion is better though unless there is some reason you cannot use it.

Colin