“undefined method” when calling helper method from controller in Rails
-
18-04-2021 - |
题
Does anyone know why I get
undefined method `my_method' for #<MyController:0x1043a7410>
when I call my_method("string") from within my ApplicationController subclass? My controller looks like
class MyController < ApplicationController
def show
@value = my_method(params[:string])
end
end
and my helper
module ApplicationHelper
def my_method(string)
return string
end
end
and finally, ApplicationController
class ApplicationController < ActionController::Base
after_filter :set_content_type
helper :all
helper_method :current_user_session, :current_user
filter_parameter_logging :password
protect_from_forgery # See ActionController::RequestForgeryProtection for details
解决方案
You cannot call helpers from controllers. Your best bet is to create the method in ApplicationController
if it needs to be used in multiple controllers.
EDIT: to be clear, I think a lot of the confusion (correct me if I'm wrong) stems from the helper :all
call. helper :all
really just includes all of your helpers for use under any controller on the view side. In much earlier versions of Rails, the namespacing of the helpers determined which controllers' views could use the helpers.
I hope this helps.
其他提示
view_context is your friend, http://apidock.com/rails/AbstractController/Rendering/view_context
if you wanna share methods between controller and view you have further options:
- use view_context
- define it in the controller and make available in view by the helper_method class method http://apidock.com/rails/ActionController/Helpers/ClassMethods/helper_method
- define it in a shared module and include/extend
Include ApplicationHelper in application_controller.rb file like this:
class ApplicationController < ActionController::Base
protect_from_forgery
include ApplicationHelper
end
This way all the methods defined in application_helper.rb file will be available in the controller.
You can also include individual helpers in individual controllers.
Maybe I'm wrong, but aren't the helpers just for views? Usually if you need a function in a controller, you put it into ApplicationController as every function there is available in its childclasses.
As said by gamecreature in this post:
- In Rails 2 use the
@template
variable. - In Rails 3 use the controller method
view_context
helpers are for views, but adding a line of code to include that helper file in ApplicationController.rb can take care of your problem. in your case, insert the following line in ApplicationController.rb:
include ApplicationHelper
As far as i know, helper :all
makes the helpers available in the views...
Try appending module_function(*instance_methods)
in your helper modules, after which you could directly call those methods on the module itself.
though its not a good practice to call helpers in controller since helpers are meant to be used at views
the best way to use the helpers in controller is to make a helper method in application_controller and call them to the controller,
but even if it is required to call the helper in a controller
then Just include the helper in the controller
class ControllerName < ApplicationController
include HelperName
...callback statements..
and call the helper methods directly to the controller
module OffersHelper
def generate_qr_code(text)
require 'barby'
require 'barby/barcode'
require 'barby/barcode/qr_code'
require 'barby/outputter/png_outputter'
barcode = Barby::QrCode.new(text, level: :q, size: 5)
base64_output = Base64.encode64(barcode.to_png({ xdim: 5 }))
"data:image/png;base64,#{base64_output}"
end
Controller
class ControllerName < ApplicationController
include OffersHelper
def new
generate_qr_code('Example Text')
end
end
hope this helps !
I had the same problem...
you can hack/bodge around it, put that logic into a model, or make a class specially for it. Models are accessible to controllers, unlike those pesky helper methods.
Here is my "rag.rb" model
class Rag < ActiveRecord::Base
belongs_to :report
def miaow()
cat = "catattack"
end
end
Here is part of my "rags_controller.rb" controller
def update
@rag = Rag.find(params[:id])
puts @rag.miaow()
...
This gave a catattack on the terminal, after I clicked "update".
Given an instantiation, methods in the model can be called. Replace catattack with some codes. (This is the best I have so far)
:helper all only opens helpers up to views.
This shows how to make a class and call it. http://railscasts.com/episodes/101-refactoring-out-helper-object?autoplay=true
Try this to access helper function directly from your controllers view_context.helper_name
You can include your helper methods into a controller with a helper
keyword syntax
class MyController < ApplicationController
helper ApplicationHelper
end