Creating a Gem that adds a rails form helper - ruby-on-rails

I'm creating a gem to add a new helper method for rails forms. My gem is a single file
lib/rails_json_field.rb
that looks like this:
require 'action_view/helpers'
require 'action_view/context'
require 'securerandom'
module ActionView
module Helpers
class FormBuilder
include ActionView::Helpers::FormTagHelper
include ActionView::Helpers::JavaScriptHelper
include ActionView::Context
def json_field_tag(method, options = {})
#function code here
end
end
end
end
ActiveSupport.on_load(:action_view) do
include ActionView::Helpers::FormBuilder
end
However when I use the method like so:
= f.json_field_tag(:some_method)
I receive the following error:
ActionView::Template::Error (undefined method `json_field_tag' for #<ActionView::Helpers::FormBuilder:0x007ffa84ab52a8>)
How do I make the method available on ActionView::Helpers::FormBuilder ?

You have defined the following class:
RailsJsonField::ActionView::Helpers::FormBuilder
You meant to monkeypatch the following class:
ActionView::Helpers::FormBuilder
That's why the error message is telling you the method is undefined; you have defined it within a class within your custom module, not within the specified class:
undefined method `json_field_tag' for #<ActionView::Helpers::FormBuilder
It's only defined in RailsJsonField::ActionView::Helpers::FormBuilder, so you get the above error.
If you want to properly monkeypatch the original code then you should look at the original code to ensure your code looks like their code:
module ActionView
module Helpers
class FormBuilder
def json_field_tag(method, options = {})
# function code here
end
end
end
end
It would be better to define this as an initializer in your Rails app, e.g., in config/initializers/json_field_tag.rb. Once you have the code working as a simple patch, then you can focus on developing it into a standalone gem that enhances ActionView.

After searching, I found a different gem that adds a FormBuilder method. I used their repo as a guide to structure my own. For others with this questions, you can view my repo and their repo here respectively:
https://github.com/dyeje/rails_json_field
https://github.com/Brantron/john_hancock

Related

undefined method in Module

I have a /lib/custom
inside I have custom.rb and custom_page.rb
custom.rb
require 'custom_page.rb'
module Custom
def self.name(params)
# logic
end
end
I've added in application.rb config.autoload_paths += %W(#{config.root}/lib)
I can't seem to call in my controllers to Custom.name(params)
NoMethodError: undefined method `name' for Custom:Module
I've tried with define the method as def Custom.name, using class << self and method_function :name yet nothing helps..
Am I missing something?
It's because of the Rails naming convention. In your rails console, try
irb(main):001:0> Custom::Custom
LoadError: Expected lib/custom/custom.rb to define Custom::Custom
Rais expects you do define module Custom::Custom (not module Custom) in lib/custom/custom.rb.
Rails sees a folder lib/custom and created an empty module Custom (doesn't respond to name method) based on convention, if you want to define module Custom, you have to write a file lib/custom.rb
The convention is
lib/custom.rb #define module Custom
lib/custom/deeper.rb #define module Custom::Deeper
lib/empty_folder/ # rails provides you an empty module EmptyFolder
BTW you don't have to require 'custom_page' in your custom.rb, if Rails sees CustomPage in your code, it will try to load the class definition file based on naming convention, given that your custom_page.rb file path follows the convention.
You can also use ActiveSupport::Concern to extend both class and instance methods. In the module just to this:
module Custom
extend ActiveSupport::Concern
included do
# everything but the class methods go here
end
module ClassMethods
# define class methods here
def name(params)
#logic
end
end
end

Monkey patching Rails

I need to monkey-patch one of the Rails core classes, specifically ActionView::Helpers::UrlHelper::ClassMethods.link_to method. As far as I remember there are some events fired when parts of Rails are loaded, how to add handlers for them? Or should I just put the code into initializer?
link_to does not appear to be in ClassMethods. From here.
In config/initializers/url_helper_extensions.rb
module ActionView
module Helpers
module UrlHelper
alias_method :_link_to, :link_to
def link_to
# Your code ...
# Call original method if you want.
_link_to
end
end
end
end

Trying to include Rails helper library in module

I have a module called Sms that I'm defining in lib/sms.rb. Within it, I have a method called Sms.chunk that uses the method word_wrap. This is part of the TextHelper library, so I am including it at the beginning of the module with include ActionView::Helpers::TextHelper:
module Sms
include ActionView::Helpers::TextHelper
def Sms.chunk
...
word_wrap
...
I am requiring this module during initialization with the line require "sms" in config/initializers/additional_libs.rb
I also have a Grape API class called TWILIO_API where I want to call Sms.chunk. However, when I do, I get undefined methodword_wrap' for Sms:Module`. I have tried including the TextHelper library in the TWILIO_API class itself, and various other ways of including it, but have had no success.
What am I doing wrong here?
The problem is that wrap_word is an instance method , and you're invoking it from a class method Sms.chunk. Make it an instance method by dropping the Sms. part. For instance, the following works:
require 'action_view'
class Test
include ActionView::Helpers::TextHelper
def test_method
word_wrap('Once upon a time')
end
end
o = Test.new
p o.test_method # "Once upon a time"

Using the Rails ApplicationHelper in Grape

I have a method defined in application_helper.rb:
def bayarea_cities
[
['San Francisco', 'San Francisco'],
['Berkeley', 'Berkeley'],
...
]
end
I'm also using Grape to create an API. It's in its own module outside the Rails app:
module FFREST
class API_V2 < Grape::API
...
I'm pretty sure Grape is a Rack app, so it doesn't have normal access to the Rails modules. When I try to call the 'bayarea_cities' method in one of the API methods, I get an undefined variable or method error. I've tried include the ApplicationHelper module with 'include ApplicationHelper', but this did not work.
How can I get access to this inside the API class?
UPDATE:
Thanks for the update Deefour. I added extend self to my Helpers module, and referenced the methods as instance/mixin methods (not as module methods), but I'm still getting the same error. In my lib/helpers.rb file I have:
module Helpers
extend self
def bayarea_cities
[
'San Francisco',
'Berkeley',
'Danville',
'Oakland',
'Daly City',
'Sunnyvale'
]
end
def us_states
['CA']
end
end
and in my API file I have:
module FFREST
class API_V1 < Grape::API
include Helpers
version 'v1', :using => :header, :vendor => 'feedingforward'
...
And of course, I have the config/initializers/helpers.rb file that says require "helpers"
But when I call the US states API method, for instance, by going to http://localhost:5000/api/states, I get:
undefined local variable or method `us_states' for #<Grape::Endpoint:0x007fd9d1ccf008>
Any ideas?
Create some lib/helpers.rb file with the contents: module Helpers; end
Move the bayarea_cities method into this module definition
Add a config/initializers/helpers.rb file containing require "helpers"
Inside the ApplicationHelpers class, add include Helpers
Inside your API_V2 class add include Helpers
You'll now have told Rails to make the Helpers module available within your application, and made bayarea_cities available as a method within both your Grape API class and your Rails app. The above are steps simply to get the point across - you need to put this common functionality in a place it can be easily accessed by any part of your application. You can (and should) use namespace your Helpers module.
Another tip: add extend self to the module to avoid the need to define everything as class methods as you mentioned in the comment
module Helpers
extend self
def bayarea_cities
#...
end
end
Finally, if you're including the module properly with include Helpers, you should be able to acces the method simply as bayarea_cities, not Helpers.bayarea_cities. If this isn't the case, you should definitely show the error you get so we can sort that out for you.

Writing Rails Gems: Proper way to add to existing rails modules?

I'm just getting started with rails gems, and wondering how best to add functionality to existing rails modules. For example, if I wanted to add a new form helper, I'd typically do something like this:
class ActionView::Helpers::FormBuilder
# My form defs in here
end
But I'm wondering if that's the most elegant way of doing things - especially if, for example, I'm going to wrap the new functionality up in a gem.
For example, suppose I'm creating the gem "MyGem", and I only want its functionality to be present if the gem is called in the controller. So in the controller I add 'include MyGem', and in the lib/my_gem.rb I'd typically do something like:
# lib/my_gem.rb
module MyGem
# My form defs in here
end
The question is: what is the standard way for overwriting defs in the ActionView::Helpers::FormBuilder module from within the MyGem module?
Cheers...
If you create a Class with inheritance of ActionView::Helpers::FormBuilder you can override all method from FormBuilder you want.
You can add other method too.
After you just need use this FormBuilder when you create your form with option :builder Or you can do an helper method like simple_form_for to call the form_for method with your builder.
If you want do in a module you need create your class in module
# lib/my_gem.rb
require 'my_gem/form_builder'
# lib/my_gem/form_builder.rb
module MyGem
class FormBuilder < ActionView::Helpers::FormBuilder
# form def
end
end
In your builder you use :builder => MyGem::FormBuilder

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