Ruby on Rails - Helper Method - Undefined Method 'Log_In' in Ruby on Rails

Ruby on rails - Helper method - undefined method `log_in' in Ruby on rails

You are missing the ApplicationController part here which includes the helper in the controller so its methods can be accessible directly:

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  include SessionsHelper
end

Undefined method when calling Helper methods in rails

def self.avatar_path(user, size = 24)
        ..
end

you are calling instance method add self before mthod will work for you.

rails “undefined method” when invoking a helper method from the view

Assuming you have Person model. here is an example:

Helper:

def sportists_gender(person)
  gender = person.gender

  if gender == "1"
    "Male"
  elsif gender == "2"
    "Female"
  end
end

Call From View.erb:

 <% @person = Person.first %> // any object according to your view.
 <%= sportists_gender(@person) %> // display result. 

undefined method on custom helper method

Helper methods from controllers aren't available in mailer views. You should put your method to a helper module, for example app/helpers/application_helper.rb:

module ApplicationHelper

    def email_confirmation_path(security_user)
      "/security_users/#{security_user.id}/email_confirmation/#{security_user.activation_code}"
    end

end

And then you should say to your mailer class to use that helper module (suppose your mailer is app/mailers/mailer.rb):

class Mailer < ActionMailer::Base
  add_template_helper(ApplicationHelper)
end

After that you'll be able to use that helper in your mailer's views.

p.s. also notice that the private modifier in Ruby doesn't restrict access to a method only to class where it is defined. Subclasses are also able to call it. Private means that a method can not be called in relation to an object like so obj.my_method but can only be implicitly called in relation to self like so my_method.

undefined method error in helper for a model

You need to extend instead of include because the method you want to call it from is a class method.

Also, just a side note, your self.quantity_this_month loads all the Expense records into memory, but it's possible to do the date filtering and counting all within a single SQL query. The below is how it's done in MySQL, this might be slightly different with other databases:

class Expense < ApplicationRecord
  extend Helpers # <~~~~~~~ changed to extend
  def self.quantity_this_month
    where(
      "DATE_FORMAT(date, '%Y/%m') = ?",
      year_month(Date.today)
    ).count
  end
end

Undefined method error when calling a helper method in controller from ActionMailer view

You should move your helper method into a separate module and then include the module into both the controller and the mailer using add_template_helper method. Then the helper methods will be available in controller and mailer views.

module SomeHelper
  def some_shared_method
    # ...
  end
end

class SomeController
  add_template_helper SomeHelper
end

class SomeMailer
  add_template_helper SomeHelper
end

Note: If you place the code into a helper module (in app/helpers directory) then you won't need to include the module into the controller as helper modules methods are available in controller views by default. However, you will still have to include the module into the mailer to make the method available in the mailer views.

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If you also need to call the helper method in the controller, you can do it using the helpers method which gives you the access to helper methods.

class SomeController
  add_template_helper SomeHelper

  def some_method
    # ...
    # calling a helper method in controller 
    helpers.some_shared_method
    # ...
  end 
end

Or you can include the module into the controller using include method for the methods to be accessible in the controller directly.

class SomeController
  include SomeHelper

  def some_method
    # ...
    # calling the included method 
    some_shared_method
    # ...
  end 
end

Rails 5: NoMethodError: undefined method `helper' for MyMailer

if it really is a Mailer as opposed to a Model, you should probably inherit from ApplicationMailer as opposed to ApplicationRecord, else it is going to be be looking for tables in your DB to back it.

class MyMailer < ApplicationMailer
   .....
end 

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