Why does Rails 4 say Missing Helper file, though it is there? - ruby-on-rails

I wrote a project in Rails 3. There are three controllers, three views, three helper files (very small project).
One of the helper files, which probably is causing the problem:
> cat helpers/my_helper.rb
module MyHelper
require 'some_gems'
...
def my_function ()
... #some functionality
end
end
Now I moved to Rails 4 (updated all the staff).
Still when just starting the app rails s -b localhost -p 3000 and going to localhost:3000 in browser I get an Exception:
AbstractController::Helpers::ClassMethods::MissingHelperError in WelcomeController#index
Missing helper file helpers/my_helper.rb
What is the problem? The file is there, why Rails still missing it?

It could be that the helper could not be loaded because of missing gems from which it is trying to require libraries. Please check that your Gemfile includes all gems that you need for this helper.

Related

Getting "Uninitialized constant" routing error when loading a view

I'm a beginner to both ruby and rails, and using Rails 5.17 to develop a web app for a class.
Creating the empty Rails project was successful, but something is going wrong when creating a new controller. I generated a new controller named cars from the root of the project, which was successful. There was a file in app/controllers named cars_controller.rb which looks like this:
class CarsController < ApplicationController
end
I added a method to this file named hello that does nothing.
I then created a file named cars.html.erb in the app/views/layouts directory. This file is a basic page of html code.
In config/routes.rb, I added the following:
get '/cars', to:: 'cars_controller#hello'
resources: cars
After all of this, I ran rails server, and opened localhost:3000 in a browser. This brings up the normal Ruby on Rails welcome page.
But when I go to localhost:3000/cars, I get the following:
Routing Error
uninitialized constant CarsControllerController
I've tried changing the name of the cars_controller.rb file. I've tried changing the name of the class in the controller file from CarsController to Cars. I've tried many different routes in routes.rb. I finally tried uninstalling Rails 5.17 and installing Rails 5.13.
I'm very confused, and I'd be grateful for any advice I can get. Thanks in advance!
One of the great things about Rails is its preference for convention over configuration. However, for this to really benefit you, you need to stick to doing things “The Rails Way” rather than your own way, wherever possible.
In this case, start by getting rid of your custom get route, and just use resources :cars.
From the command line, run rake routes (you might be able to run rails routes on your rails version too) and see the routes that it has created for you.
Now, rename the method you added to your CarsController from hello to index.
Move your hello.html.erb file from app/views/layout to app/views/cars/index.html.erb.
Finally, start the rails server (rails start) and load the url http://localhost:3000/cars in your browser.
—-
Note that templates in app/views/layout have a special purpose. These are used to apply a general template to your views. Look up the use of layout within a controller for more details
I think you have an error in how you had defined your route - you don't need _controller.
Instead, try this:
get '/cars', to: 'cars#hello'
Also, keep in mind that in your cars directory you need the view: hello.html.erb

Rails 3 trouble with namespaces & custom classes (uninitialized constant)

I have a file in my Rails 3.2.11 project called app/queries/visible_discussions.rb which looks like the following:
class VisibleDiscussions
...
end
I'd like to namespace the query so that I can call it using something like Queries::VisibleDiscussions so I tried to do the following:
module Queries
class VisibleDiscussions
...
end
end
However, I'm getting a uninitialized constant Queries (NameError) when I try to call Queries::VisibleDiscussions from the rails console.
Any ideas?
if you add lib to your autoload_paths then it will respect the namespacing under lib - lib/query/visible_discussions.rb
or create a new dir under app - say src and then nest your code there - app/src/query/visible_discussions.rb
i would use the 3rd style in your post for either of these, i.e.
module Query
class VisibleDiscussions
...
end
end
both of these solutions are annoying to me, there might be a way to tell rails to namespace directories under app, but i have no clue how it would be done
Rails needs to know what directories to load (a part from the defaults). Try:
#config.application.rb
config.autoload_paths += %W(#{config.root}/queries)

What is the simplest way to make a group of methods available to several Rails applications

tl;dr
What's a simple way I can create a view helpers module I can use in many apps?
What file, located where, loaded how?
I'm on Rails 2.3.11.
I have a bunch of view helper methods. Here's an example of one of them:
# Render form input fields to add or edit a ZIP code.
def render_zip_code_fields( model_instance )
# Bla bla bla ...
end
I have about 20 or so that I've developed over the years and often use in various applications. I'd like to wrap them all up in one file that I can just drop into and app and then be able to call them in my views.
Why not just copy-and-paste them into application_helper.rb? That just doesn't feel right to me. It seems like it should be a separate file.
In fact I tried creating in /lib...
# /lib/my_view_helpers.rb
module MyViewHelpers
# ...
end
And then in application_helper.rb I put...
include MyViewHelpers
But I got a lot of "uninitialized constant MyViewHelpers errors. Maybe a syntax error? I don't think I need to require my_view_helpers.rb first because it's in /lib. Everything in there gets loaded automatically, right?
So what's the right way to do this optimizing for simplicity?
Sorry this is so long. I get verbose when I'm tired.
As of Rails 3, /lib is no longer on the default load path. You will need to put the following line in the Application class in config/application.rb.
config.autoload_paths += ["#{config.root}/lib"]
An alternative would be to drop the file in app/helpers since it is a helper, after all.

Converting Rails 2 plugin to Rails 3 gem

So there's this great plugin I've gotten used to using in my Rails 2 projects called Bootstrapper. It essentially duplicates the functionality of the seeds.rb file, but I like it because it lets you break up your bootstrap process into concise chunks.
Anyway, I've gone so far as to fork the project and attempt to turn it into a Rails 3 gem. I've been able to get the gem to initialize and register the rake tasks and generators OK. However, I'm running into a problem with the Bootstrapper class itself. It won't load in the Rails project unless it's in a module.
That is, if I place the Bootstrapper class in a file by itself and require that file in my Railtie, then in my Rails app, it can't find the Bootstrapper class. If I put the class in a module and call Bootstrapper::Bootstrapper everything is peachy.
The code that actually requires the Bootstrapper class is this:
ActiveSupport.on_load :active_record do
require 'bootstrapper/bootstrapper'
end
The source is available here:
http://github.com/jrmehle/bootstrapper/tree/make_gem
Autoload paths actually has an annoying feature of following filesystem paths. For example in your lib or extras (depending on what you autoload) you might have the following file structure:
lib/bootstrapper/bootstrapper.rb
# in this case, Bootstrapper::Bootstrapper.class = Class in rails c
# ie: you don't get a NameError exception
More specifically,
lib/bootstrappers/bootstrapper.rb
# Bootstrapper::Bootstrapper => NameError
# Bootstrappers::Bootstrapper => works
If you really want the other way, you can move everything into your lib/bootstrapper.rb source file but meh, I don't like doing that, that's not how gems are organized. In rails3, you'll find the autoloading pretty nice once you use modules everywhere (which can be painful).
Rails3 uses /extras instead of /lib but it's not required, it's just the default (commented out) from rails new. To switch, you just autoload extras instead of lib.

Rails: filter defined in lib file required in environment.rb disappears from filter_chain in production environment. Why?

In my rails application, I have a file in lib that, among other things, sets up a filter that runs on all controllers.
When running under development environment, everything runs fine. However, under production the filter goes missing. Funny thing is, by inspecting the filter_chain, I noticed other filters remain, eg. those defined in plugins, or later in the specific controller class.
I've tested this with both rails edge and v2.3.0.
Testing update:
I've now tested with older rails and found the issue to be present back to v2.1.0, but not in v2.0.5, I've bisect them and found the 986aec5 rails commit to be guilty.
I've isolated the behavior to the following tiny test case:
# app/controllers/foo_controller.rb
class FooController < ApplicationController
def index
render :text => 'not filtered'
end
end
# lib/foobar.rb
ActionController::Base.class_eval do
before_filter :foobar
def foobar
render :text => 'hi from foobar filter'
end
end
# config/environment.rb (at end of file)
require 'foobar'
Here's the output I get when running under the development environment:
$ script/server &
$ curl localhost:3000/foo
> hi from foobar filter
And here's the output for the production environment:
$ script/server -e production &
$ curl localhost:3000/foo
> not filtered
As alluded to before, it works fine for any environment when I do the same thing via plugin. All I need is to put what's under lib/foobar.rb in the plugin's init.rb file.
So in a way I already have a workaround, but I'd like to understand what's going on and what's causing the filter to go missing when in production.
I conjecture it's something in the different ways Rails handles loading in the different environments, but I need to dig deeper.
update
Indeed, I've now narrowed it down to the following config line:
config.cache_classes = false
If, in production.rb, config.cache_classes is changed from true to false, the test application works properly.
I still wonder why class reloading is causing such thing.
Frederick Cheung on the Rails list had the answer:
Because cache_classes does a little more than just that. The way
before filters work, if Foo < Bar then only those filters defined in
Bar at that point will be inherited by Foo - adding them to Bar at a
later date will not do anythingn
In development mode, the app starts, your file is required, the filter
added to ActionController::Base. Later the first request comes along,
the controller is loaded and it inherits that filter.
When cache_classes is true then all of your application classes are
loaded ahead of time. This happens before your file is required, so
all of your controllers already exist when that file is run and so it
has no effect. You could solve this by requiring this file from an
initializer (ensuring it runs before app classes are loaded), but
really why wouldn;t you just put this in application.rb ?
Fred
My real case was actually way more involved, and this is the way I found to solve the issue:
config.after_initialize do
require 'foobar'
end
The after_initialize block runs after the framework has been initialized but before it loads the application files, hence, it'll affect ActionPack::Base after it's been loaded, but before the application controllers are.
I guess that's the generally safe way to deal with all the preloading that goes on in production.
Drop a ruby script in
RAILS_ROOT\config\initializers
that contains
require "foobar.rb"
This invokes the before_filter for me.

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