In my rails application I have a teams model. My route.rb file for teams looks like this:
resources :teams
In my teams_controller.rb file the line team_path(Team.first.id) works however the team_path url helper is not recognized in my model team.rb. I get this error message:
undefined local variable or method `team_path' for # <Class:0x00000101705e98>
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-4.1.1/lib/active_record/dynamic_matchers.rb:26:in `method_missing'
I need to find a way for the model to recognize the team_path path helper.
You should be able to call the url_helpers this way:
Rails.application.routes.url_helpers.team_path(Team.first.id)
Consider solving this as suggested in the Rails API docs for ActionDispatch::Routing::UrlFor:
# This generates, among other things, the method <tt>users_path</tt>. By default,
# this method is accessible from your controllers, views and mailers. If you need
# to access this auto-generated method from other places (such as a model), then
# you can do that by including Rails.application.routes.url_helpers in your class:
#
# class User < ActiveRecord::Base
# include Rails.application.routes.url_helpers
#
# def base_uri
# user_path(self)
# end
# end
#
# User.find(1).base_uri # => "/users/1"
In the case of the Team model from the question, try this:
# app/models/team.rb
class Team < ActiveRecord::Base
include Rails.application.routes.url_helpers
def base_uri
team_path(self)
end
end
Here is an alternative technique which I prefer as it adds fewer methods to the model.
Avoid the include and use url_helpers from the routes object instead:
class Team < ActiveRecord::Base
delegate :url_helpers, to: 'Rails.application.routes'
def base_uri
url_helpers.team_path(self)
end
end
Models are not supposed to be dealing with things like paths, redirects or any of that stuff. Those things are purely constructions of the view or the controller.
The model really should be just that; a model of the thing that you are creating. It should fully describe this thing, allow you to find instances of it, make changes to it, perform validations upon it... But that model wouldn't have any notion of what path should be used for anything, even itself.
A common saying in the Rails world is that if you're finding it difficult to do something (like call a path helper from a model) you are doing it wrongly. Take this to mean that even if something is possible, if it is hard to do in Rails it is likely not the best way to do it.
to add on the previous answer you can use Rails.application.routes.url_helpers just add in route :as like the following example:
get "sessions/destroy/:param_id", as: :logout
so you can use it as following:
Rails.application.routes.url_helpers.logout_path(:param_id => your_value)
Hopefully, this would help
Related
I need some help with my plugin. I want to extend ActiveRecord::Base with a method that initializes another method that can be called in the controller.
It will look like this:
class Article < ActiveRecord::Base
robot_catch :title, :text
...
end
My attempt at extending the ActiveRecord::Base class with robot_catch method looks like following. The function will initialize the specified attributes (in this case :title and :text) in a variable and use class_eval to make the robot? function available for the user to call it in the controller:
module Plugin
module Base
extend ActiveSupport::Concern
module ClassMethods
def robot_catch(*attr)
##robot_params = attr
self.class_eval do
def robot?(params_hash)
# Input is the params hash, and this function
# will check if the some hashed attributes in this hash
# correspond to the attribute values as expected,
# and return true or false.
end
end
end
end
end
end
ActiveRecord::Base.send :include, Plugin::Base
So, in the controller, this could be done:
class ArticlesController < ApplicationController
...
def create
#article = Article.new(params[:article])
if #article.robot? params
# Do not save this in database, but render
# the page as if it would have succeeded
...
end
end
end
My question is whether if I am right that robot_catch is class method. This function is to be called inside a model, as shown above. I wonder if I am extending the ActiveRecord::Base the right way. The robot? function is an instance method without any doubt.
I am using Rails 3.2.22 and I installed this plugin as a gem in another project where I want to use this functionality.
Right now, it only works if I specifically require the gem in the model. However, I want it the functionality to be included as a part of ActiveRecord::Base without requiring it, otherwise I'd have to require it in every model I want to use it, not particularly DRY. Shouldn't the gem be automatically loaded into the project on Rails start-up?
EDIT: Maybe callbacks (http://api.rubyonrails.org/classes/ActiveSupport/Callbacks/ClassMethods.html) would be a solution to this problem, but I do not know how to use it. It seems a bit obscure.
First, I would suggest you make sure that none of the many many built in Rails validators meet your needs.
Then if that's the case, what you actually want is a custom validator.
Building a custom validator is not as simple as it might seem, the basic class you'll build will have this structure:
class SpecialValidator < ActiveModel::EachValidator
def validate_each(record, attribute, value)
# Fill this with your validation logic
# Add to record.errors if validation fails
end
end
Then in your model:
class Article < ActiveRecord::Base
validates :title, :text, special: true
end
I would strongly suggest making sure what you want is not already built, chances are it is. Then use resources like this or ruby guides resources to continue going down the custom validator route.
Answer
I found out the solution myself. Bundler will not autoload dependencies from a gemspec that my project uses, so I had to require all third party gems in an engine.rb file in the lib/ directory of my app in order to load the gems. Now everything is working as it should.
Second: the robot_catch method is a class method.
In my case I get an instance of a resource and I have to find out, whether it's model class represents a singular or plural resource.
I digged through Rails.application.routes and it's instance variables but did not find any possibility to solve this problem.
Update:
I am using polymorphic_path helpers with anonymous model instances in a gem that includes some modules into models and controllers. The final goal is to provide some automatisms for REST controllers and models and provide pathes / routes of the current model/instance as well as it's ancestors.
My latest attempts looked something like that:
Rails.application.routes.instance_variable_get(:#router).instance_variable_get(:#routes).instance_variable_get(:#named_routes).delete_if{|k,v| !k.match(/my_model_name_as_downcased_string_here/)}.values.map{|v| v.instance_variable_get(:#defaults)}.map{|h| h[:action]}
In the hope it would bring up action :index for plural models and :show for singular. There MUST be a way to make use of introspection to find out whether a model is a singular one, I simply do not find the catch.
Since I did not find any way to find out, whether a resource is singular or plural, I build something on my own. The most secure way IMHO is to hook into route creation direcly. Here's what I did in case anyone encounters the same problem:
# alias :resource method of Rails routing mapper and remember which resourses
# are setup as singular
module ActionDispatch::Routing::Mapper::Resources
def resource_with_singular_recognizer *res, &block
Rails.application.instance_variable_set(:#sr, ((Rails.application.instance_variable_get(:#sr) || []).push res.first).uniq)
resource_without_singular_recognizer *res, &block
end
alias_method_chain :resource, :singular_recognizer
end
# define a model wide method :singular_resource? that checks the previously
# setup singular resource flag
module ClassMethods
def singular_resource?
Rails.application.instance_variable_get(:#sr).include? self.to_s.downcase.to_sym
end
end
# include :singular_resource? method into all model classes
module Mongoid::Document
def self.included base
base.class_eval do
extend ClassMethods
end
end
end
I know :alias_method_chain is not the best choice here, feel free to find a better solution.
I'm writing an app where I need to override the default routing helpers for a model. So if I have a model named Model, with the corresponding helper model_path() which generates "/model/[id]". I'd like to override that helper to generate "/something/[model.name]". I know I can do this in a view helper, but is there a way to override it at the routing level?
You can define to_param on your model. It's return value is going to be used in generated URLs as the id.
class Thing
def to_param
name
end
end
The you can adapt your routes to scope your resource like so
scope "/something" do
resources :things
end
Alternatively, you could also use sub-resources is applicable.
Finally you need to adapt your controller as Thing.find(params[:id]) will not work obviously.
class ThingsController < ApplicationController
def show
#thing = Thing.where(:name => params[:id).first
end
end
You probably want to make sure that the name of your Thing is unique as you will observe strange things if it is not.
To save the hassle from implementing all of this yourself, you might also be interested in friendly_id which gives you this and some additional behavior (e.g. for using generated slugs)
You need the scope in routes.rb
scope "/something" do
resources :models
end
My project name is clog, so I named my models and controllers like this: Clog::User Clog::Userscontroller.
Is this naming convention mandatory?
No, in a conventional Rails project, that's not necessary. Just name your models and controllers the usual way, like eg User or UsersController.
The other thing is that, when your project grows in size, you may need to organize your models into submodules. One approach to do so is extending your models with app concerns, as show eg here or here.
As for organizing controllers, one approach is to create a module in the lib directory, which you then include in your ApplicationController, like so:
In lib/authentication.rb:
module Authentication
def self.included(base)
base.send :before_filter, :login_required
base.send :helper_method, :current_user, :logged_in?
end
def current_user
#current_user ||= User.find_by_remember_token(cookies[:remember_token]) if cookies[:remember_token].present?
end
#...
end
In app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
include Authentication
#...
end
For this to work, you need to add
config.autoload_paths << "#{config.root}/lib"
to your config/application.rb file
However, if you plan to build your Rails project as a Rails Engine, you may want to follow some naming convention. A good example of a Rails Engine is forem.
Yes, following the naming convention helps a great deal because not only does rails use it to generate other names, but other gems as well.
Specific to your question, you may be asking if you need to name the controller as UserController given that your model is called User. That is not necessary at all, and you may call it anything else if it better fits your purpose.
In this case, you will probably want to create a few controllers like so:
My::AccountController # for e.g.. /my/account
Admin::UsersController # for e.g. /admin/users/1
For a user, you refer to your own user record, as 'your account' so this makes more sense. However, the administrator's perspective would be to manage user records. You may also name a controller one thing and serve it under a different route. In your routes file, you may do this:
namespace :admin do
resources :users, :path => "user-accounts"
end
To reiterate, your model name need not match up to the controller name. They are only named similarly by association: UserController is understood to handle User records.
In models and controllers, we often use Rails macros like before_validation, skip_before_filter on top of the class definition.
How is this implemented? How do I add custom ones?
Thanks!
They're just standard Ruby functions. Ruby's flexible approach to syntax makes it look better than it is. You can create your own simply by writing your method as a normal Ruby function and doing one of the following:
putting it somewhere that's accessible by your controllers such as application.rb
putting it in a file and requiring it in.
mixing the code into a class via the Ruby include keyword.
That last option is great for model classes and the first option is really only for controllers.
An Example
An example of the first approach is shown below. In this example we add code into the ApplicationController class (in application.rb) and use it in the other controllers.
class BusinessEntitiesController < ApplicationController
nested_within :Glossary
private
# Standard controller code here ....
The nested_within provides helper functions and variables to help identify the id of the "parent" resource. In effect it parses the URL on the fly and is accessible by every one of our controllers. For example when a request comes into the controller, it is automatically parsed and the class attribute #parent_resource is set to the result of a Rails find. A side effect is that a "Not Found" response is sent back if the parent resource doesn't exist. That saves us from typing boiler plate code in every nested resource.
That all sounds pretty clever but it is just a standard Ruby function at heart ...
def self.nested_within(resource)
#
# Add a filter to the about-to-be-created method find_parent_id
#
before_filter :find_parent_id
#
# Work out what the names of things
#
resource_name = "#{resource.to_s.tableize.singularize}"
resource_id = "#{resource_name}_id"
resource_path = "#{resource.to_s.tableize}_path"
#
# Get a reference to the find method in the model layer
#
finder = instance_eval("#{resource}.method :find_#{resource_name}")
#
# Create a new method which gets executed by the before_filter above
#
define_method(:find_parent_id) do
#parent_resource = finder.call(params[resource_id])
head :status => :not_found, :location => resource_path
unless #parent_resource
end
end
The nested_within function is defined in ApplicationController (controllers/application.rb) and therefore gets pulled in automatically.
Note that nested_within gets executed inside the body of the controller class. This adds the method find_parent_id to the controller.
Summary
A combination of Ruby's flexible syntax and Rail's convention-over-configuration makes this all look more powerful (or weirder) than it actually is.
Next time you find a cool method, just stick a breakpoint in front of it and trace through it. Ahh Open Source!
Let me know if I can help further or if you want some pointers on how that nested_within code works.
Chris
Chris's answer is right. But here's where you want to throw your code to write your own:
The easiest way to add Controller methods like that is to define it in ApplicationController:
class ApplicationController < ActionController::Base
...
def self.acts_as_awesome
do_awesome_things
end
end
Then you can access it from individual controllers like so:
class AwesomeController < ApplicationController
acts_as_awesome
end
For models, you want to reopen ActiveRecord::Base:
module ActiveRecord
class Base
def self.acts_as_super_awesome
do_more_awesome_stuff
end
end
end
I personally would put that in a file in config/initializers so that it gets loaded once, and so that I know where to look for it always.
Then you can access it in models like so:
class MySuperAwesomeModel < ActiveRecord::Base
acts_as_super_awesome
end