Unfortunately official guide for creating Rails plugins is outdated: http://guides.rubyonrails.org/plugins.html and I didn't find any good tutorial for creating engines only this code: https://github.com/mankind/Rails-3-engine-example and enginex https://github.com/josevalim/enginex were helpful.
So... what are differences between plugins and engines in Rails 3? (I'm thinking of plugins and engines with controllers and views)?
And how can I create plugin with views and controllers? Or maybe in Rails 3 it's better to use engines? Can I use main app model (for example user model, logged user information) inside my engine?
Engines are just required as gems in your app. Since Rails 3.1 you even don't have to require their assets such as .css or .js
In Rails 2.x, Engines didn't exist, so plugins enabled people to have these functionalities but all code was copied inside the app.
Related
I have a rails application that is kind of similar to the active_admin gem. I want to make this existing application into a gem.
I know that you can generate a gem with:
bundler gem gem_name_here
This command creates an empty gem. Which is fine I suppose, I just don't know where to put all my code.
You're ostensibly supposed to put all of your code in the /lib directory. However, my application has an assets pipeline and an app directory with all my models, controllers, and views. I don't know where to place all of these directories in the gem. Any thoughts or ideas?
If you need me to share any code, I'll gladly share it.
You're describing a rails engine. Engine is a miniature rails application that can be used inside other rails app. For more details see official rails guide
I am currently developing a rails 4 based media streaming app and wanted to know if i could have the rails app as a kind of source code and bundle it into a gem for distribution? is there some sort of easy solution for this? or do i have to roll my own?
From your description, I think you can do this via an Engine. From the Rails docs:
Engines can be considered miniature applications that provide functionality to their host applications.
...
Engines are also closely related to plugins where the two share a common lib directory structure and are both generated using the rails plugin new generator. The difference being that an engine is considered a "full plugin" by Rails as indicated by the --full option that's passed to the generator command, but this guide will refer to them simply as "engines" throughout. An engine can be a plugin, and a plugin can be an engine.
Read more at http://guides.rubyonrails.org/engines.html
I am trying to use Spree with my RoR application. Ok, I do follow all those guides and FAQs on official website when I want to customize something. That's ok and no problem with it. One question, to which I could not find a clue -- how is that possible, that there is nothing in apps/view, apps/models folders, but it's still working? I mean, yes, I can create something in these folders and redefine the behavior of my views (actually, this is one of the ways of customization), but I really want to understand the internals. I am pretty new to Rails and got used to classic app folder structure.
what you are wondering about is the magic of Rails Engines.
Ruby on Rails allows you to define Engines (your app is one too) and when it looks for views/controllers/etc.. all mounted engines are part of the search path.
So the view is inside the Spree gem, not visible to you - but it still looks in there.
If you put something in your view folder with the same name, it will take precedence over the views in the Rails engine you have in the Gem.
Here is a good guide on how Engines work in Rails:
http://edgeguides.rubyonrails.org/engines.html
One good example of these Engines is the jQuery-rails Gem you probably use inside your Application.
It has no code at all (except for some fallbacks for Rails 3.0 and below that don't have an asset pipeline), but the jQuery.js file in the app/assets/javascripts folder. And since the engine is in the load path you can require the asset that's in there..
The engine itself has the same folder structure as your app (app/views, app/controllers ...)
You can look at the internal structure of Spree here: https://github.com/spree/spree/tree/master/core/app
I have features I would like to be portable between my own Rails applications.
I wonder if I should create a gem or a plugin for each feature I want to be portable (sharable).
They are just for Rails (for now) because they include css, html, js and image files.
But I have been wondering, the things provided with plugins could be provided with gems too but not the opposite? So maybe it's better to learn how to create gems, because then you I don't have to learn how to create both gems and plugins? And gems seem to be more popular these days.
But then, from what I can understand one gem is shared between all rails app in the OS. So that means I can not customize it for each Rails app right? In that case, maybe creating a plugin is better cause it should be allowed to customize (editing css, js etc) each feature and to have it stored inside the Rails app itself and not in the OS level.
Some advices would be appreciated!
UPDATE:
So gem works great with css, html, js and image files? In a plugin I think you can have a MVC, your own models, views and controllers. Quoted from Rails guides "Storing models, views, controllers, helpers and even other plugins in your plugins". Is this possible too in a gem? Eg. I want to add a extension that gives me a nice Shopping cart (with own migrations, mvc, asset files) that will be hooked into the current Rails app. Is this possible as gem or only as plugin?
You're right that gems offer a little more than plugins. Versioning and dependencies on other gems being the main ones for me.
One gem needn't be shared across everything using ruby. You can install multiple versions of a single gem and specify in your environment.rb that a gem requires a specific version. E.g.
config.gem 'my-gem', :version => '1.2.3'
Also you can freeze gems into your rails application so that you know you are working with a specific version.
You might want to look at the jeweler gem which makes creating your own gems easier.
UPDATE
To include CSS, javascript etc I think you'll need to make an Rails engine which can then be bundled as a plugin or a gem. I've not done this but there's some coverage here and here.
The push with Rails 3 seems to be towards gems and away from plugins as a lot of support has been added to make gems work as well or better than plugins ever did. A well constructed gem is a great thing to have and share between different applications, and also reduces the amount of testing you will have to do since you can test the gem thoroughly before integration.
For extensions to Rails that use CSS, HTML and other assets, it might be that you need to build an engine to bundle this all up and allow it to fit neatly into an application.
As of Rails 4, plugins will no longer be supported.
Gems are the way forward.
According to the Ruby on Rails 2.3 Release Notes...
if your plugin has an app folder, then app/[models|controllers|helpers] will automatically be added to the Rails load path. Engines also support adding view paths now, and ActionMailer as well as Action View will use views from engines and other plugins.
There is supposed to be some way to make Rails aware of the app/views of your Rails engine, in 2.3. However, there is virtually no documentation on how this feature really works, that I can seem to find.
Can anyone help me get my view paths working from the context of a Rails Engine scenario?
IMPORTANT: The big issue is not with views as much as it is with partials. I need to be able to load partials from the view path of a rails engine.
Thanks!!
Turns out, I just needed to restart. This is done automatically by virtue of me defining a proper views directory within the nested app.
Durr!