Helpers in controller - Rails 3

Question

I migrated from rails 2.x to 3.x. Now when calling a controller method throws

undefined method `my_helper_method' for nil:NilClass

MyController.rb

class MyController < ApplicationController
    def foo
      @template.my_helper_method
    end
end

MyControllerHelper.rb

class MyControllerHelper
    def my_helper_method
      puts "Hello"
    end
end

ApplicationController

class ApplicationController < ActionController::Base
   helper :all
end

How to get this working?

score 3 · Accepted Answer · edited May 23 '17 at 12:06

3

This is actually answered in another SO post: Rails 3: @template variable inside controllers is nil

Essentially, you can replace @template with view_context

edited May 23 '17 at 12:06

Community

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answered Mar 23 '12 at 00:20

Melinda Weathers

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pdu · Answer 2 · 2012-01-18T10:37:38.423

@template is an object, in your case nil. If this object doesn't has the method (my_helper_method) in it, you cannot call it (especially not if it is nil).

Methods defined in helpers are called like regular methods. But not in controllers, they are called in views. Your helper :all just makes all helpers available to the views.

So, in your view: my_helper_method :arg1, :arg2

IF you need a method for your object (@template), you need to give your object this method.

Example:

class Template < ActiveRecord::Base

  def my_helper_method
    # do something on a template instance
  end

end


class MyController < ApplicationController
  def foo
    @template = Template.first
    @template.my_helper_method # which actually isn't a helper
  end
end

What helpers do:

module MyHelper
  def helper_method_for_template(what)
  end
end

# in your view
helper_method_for_template(@template)

Mixing in a helper (be aware of having a mess in your code when mixing view helpers with views and models)

class Template < ActiveRecord::Base
  include MyHelper

  # Now, there is @template.helper_method_for_template(what) in here. 
  # This can get messy when you are making your helpers available to your
  # views AND use them here. So why not just write the code in here where it belongs
  # and leave helpers to the views? 
end

But you are migrating to rails3. I don't know why it is working, but helpers are supposed to help in your views. If you want to include helpers in your controller, do `include MyControllerHelper` in your controller. However, these are still "usual" methods and not instance methods for an object ( e.g. `@template`). You could make them available for this object when mixing in the helper methods into your Model/Instance Base. But this would not really follow the convention. — pdu, Jan 18 '12 at 10:29
you are better off `migrating` and not `patching-everything-so-the-old-things-which-are-not-good-are-still-working`. If you really want to do the second one, stay on rails 2.x. I updated the answer, have a look. What you want is to define those methods inside your Model or whatever `@template` is created of. — pdu, Jan 18 '12 at 10:33

Helpers in controller - Rails 3

2 Answers2