I have a mountable engine called Blog that apps can use.
What's the best way to allow apps that use the engine to set a configuration variable like site_name (so that the engine can display it in the design)?
Update:
I've seen some gems create a 'config/initializers/gem_name.rb' file. Is there any specification on how to:
Create a file like that on the engine's side
Copy it into the app's side
How to access those set variables on the engine's side?
I tried creating Blog.site_name = "My Site" in the app's config/initializers/blog.rb file but get an Undefined method error.
Figured out an even better solution that also allows you to set default values (incase the app using the engine doesn't specify a config)...
Create config variables in your app's /config/initializers/blog.rb like this:
Blog.setup do |config|
config.site_name = "My Site Name"
end
In your engine's /lib/blog/engine.rb set default values like this:
module Blog
self.mattr_accessor :site_name
self.site_name = "Site Name"
# add default values of more config vars here
# this function maps the vars from your app into your engine
def self.setup(&block)
yield self
end
end
Now you can simply access the config variables in your engine like this:
Blog.site_name
Much cleaner.
After a lot of testing and looking into existing gems, here is what works in Rails 4:
Considering your engine's name is Blog:
In your engine's /lib/blog/engine.rb put in this:
module Blog
def self.setup(&block)
#config ||= Blog::Engine::Configuration.new
yield #config if block
#config
end
def self.config
Rails.application.config
end
end
In your app, create a file called /config/initalizers/blog.rb and set config vars like this:
Blog.setup do |config|
config.testingvar = "asdfasdf"
end
Then you can access these config variables ANYWHERE in your engine like this:
Blog.config.testingvar
Hope this helps someone. There is very little documentation on this right now so it was all trial and error.
I know this is a fairly old post, but in the event someone in the future finds this, I'd like to recommend the Angostura gem for passing dependencies into a Rails engine. To use it, assuming my engine is called 'Blog' and I want to access a variable called 'site_name', the engine's lib/blog.rb looks something like:
require "blog/engine"
require "angostura"
module Blog
include Angostura::Dependencies
dependency :site_name
end
In my main app, in config/initializers/blog.rb, I added
Blog.setup do |config|
config.site_name = "My site name"
end
Now, I can access site_name in my engine by calling Blog.site_name.
I'd like to point out that defaults are also supported, so you could do something like dependency site_name: 'Default site name' in lib/blog.rb. Furthermore, you can pass in whole classes as dependencies by sending it stringified classnames, like config.my_class = 'MyClass'.
For posterity, in order to use the gem, I added s.add_dependency "angostura", "0.6.0" in my engine's gemspec, and then ran bundle install.
Related
We're building a Chat service, which people are able to use from within their code.
Amongst the tools we're building, we've made a Ruby gem to allow people to quickly add a Chat window to their Ruby web-application.
We'd like to create a Rails-specific wrapper, though, because currently the user has to manually call .html_safe.
How is it possible to use these Rails-specific features from within a Ruby gem? I've heard this might be called 'Railsties' but I have not been able to find any comprehensive documentation about these, and how to use them.
Specifically, we'd like to:
Call html_safe on some string output so the user does not have to do this manually.
Put some configuration settings in a file in config/initializers/some_name.rb rather than having to specify these inline.
Potentially create a generator that the user can run to fill this initializer automatically.
How can we use these features? Is there some other gem-dependency we can include in our gem to access these features?
Engines can be considered miniature applications that provide
functionality to their host applications. A Rails application is
actually just a "supercharged" engine, with the Rails::Application
class inheriting a lot of its behavior from Rails::Engine.
https://guides.rubyonrails.org/engines.html
An engine can contain models, controllers, routes, generators, middleware and any arbitrary code that you can mount in the host application. Engines are usually packaged as gems.
Devise for example is a rails engine that provides authorization.
Rails has a generator command for creating engines:
rails plugin new chatty --mountable
For this example lets call it chatty.
Since an engine is mounted in a Rails application you have full access to the Rails stack (such as .html_safe). This also means that you test engines by mounting them in a dummy application.
If you have packaged the application as a gem than you simply mount it in the host application by adding it to the Gemfile.
To make your engine configurable you can follow the "MyGem.configure pattern":
# lib/chatty.rb
module Chatty
class << self
attr_accessor :configuration
end
def self.configure
self.configuration ||= Configuration.new
yield(configuration)
end
class Configuration
attr_accessor :foo
def initialize
#foo = 'some_value'
end
end
end
To create a user configuration file you use a generator:
# lib/generators/chatty/install/install_generator.rb
module Chatty
class InstallGenerator < Rails::Generators::Base
source_root File.expand_path('templates', __dir__)
desc "Creates a Chatty initializer."
def copy_initializer
template 'chatty.rb', 'config/initializers/chatty.rb'
end
end
end
And a code template:
# /lib/generators/chatty/install/templates/chatty.rb
Chatty.configure do |config|
config.foo = "bar"
end
You can now run rails g chatty:install and it will create the file in the host application.
I am new to Ruby on rails. i am using rails 4.1.6 and what i want is to make log of all the process in one text file (like index page accessed, view page access etc..). for that i want to create common function, in which i can pass my text as agrs, i had do some R&D on that and i found this : In Rails, where to put useful functions for both controllers and models, but it seems that it is not working with active admin resources. so, for active admin controller and model, i have to create any other modules (i.e. on other location let say /admin/) or anything else i have to do ?
is there any global location that we can use in active admin like component in cakephp.
thanks
EDIT
app/admin/driver.rb
ActiveAdmin.register User, as: 'Driver' do
...
...
index :download_links => false do
...
...
#call function to maintain log something like,
take_note('action performed')
end
A global method feel like a code smell to me. Instead I would create a Note class or module. This doesn't pollute the global name space and is easier to test in isolation.
I would add code like this in a initializer:
# in config/initializers/note.rb
module Note
def self.take(message)
# log `message`
end
end
It could be used in your controller like this:
index :download_links => false do
# ...
Note.take('action performed')
end
Please note that you need to restart your server when changing files in the config folder.
Easiest way is to create a file in the config/initializers folder - these will be autoloaded.
You could also write it in application.rb, though I recommend only doing this for configuration.
A common pattern is to add lib/ to the autoload path so any custom files there can be used - see Auto-loading lib files in Rails 4
It's maybe worth mentioning that you can in fact access your models from anywhere as well.
for your comment
here's a generic class which you can write in lib/ if you add it to your autoload path
class MyClass
def self.my_class_method
puts "i was called"
end
end
Then calling it from anywhere else ...
MyClass.my_class_method
I wanted to use this api: https://github.com/coinbase/coinbase-ruby and the first step is to initialize the API, like this:
coinbase = Coinbase::Client.new(ENV['COINBASE_API_KEY'], ENV['COINBASE_API_SECRET'])
I was wondering what the best place to put this code is, and how would I access it if I put it "there"? I want this variable (coinbase) to be accessible ANYWHERE in the application.
Thanks!
The answer to this question really depends on your use case and your approach. My geral recommendation, however, is to create a Service Object (in the DDD sense) (see the section named "Domain Objects Should Not Know Anything About Infrastructure Underneath" in that link), that handles all communication with the Coinbase API. And then, within this service object, you can simply initialize the Coinbase::Client object once for however many times you call into it. Here's an example:
# app/services/coinbase_service.rb
class CoinbaseService
cattr_reader :coinbase_client, instance_accessor: false do
Coinbase::Client.new(ENV['COINBASE_API_KEY'], ENV['COINBASE_API_SECRET'])
end
def self.do_something
coinbase_client.do_something_in_their_api
end
def self.do_something_else
coinbase_client.do_something_else_in_their_api
end
end
So then you might do, e.g.:
# From MyController#action_1
if CoinbaseService.do_something
# ...
else
# ...
end
Or:
# From MyModel
def do_something
CoinbaseService.do_something_else
end
To get the service object working, you may need to add app/services to your autoload paths in application.rb file. I normally just add this:
# config/application.rb
config.autoload_paths += %W(#{config.root}/app)
I find this Service Object approach to be very beneficial organizationally, more efficient (only 1 invocation of the new Coinbase client needed), easier to test (easy to mock-out calls to Coinbase::Client), and simply joyful :).
One way to go about having a global variable can be done as similar as initializing redis in a Rails application by creating an initializer in config/initializers/coinbase.rb with:
$coinbase = Coinbase::Client.new(ENV['COINBASE_API_KEY'], ENV['COINBASE_API_SECRET'])
Now, you can access $coinbase anywhere in the application!
In the file config/initializers/coinbase.rb
Rails.application.config.after_initialize do
CoinbaseClient = Coinbase::Client.new(
Rails.application.credentials.coinbase[:api_key],
Rails.application.credentials.coinbase[:api_secret])
end
In place of the encrypted credentials, you could also use environment variables: ENV['COINBASE_API_KEY'], ENV['COINBASE_API_SECRET']
The above will make the constant CoinbaseClient available everywhere in your app. It will also ensure all your gems are loaded before the client is initialized.
Note: I am using Rails 6.1.4.4, and Ruby 2.7.5
I am new to Rails and come from a ColdFusion background, where we would store global / site-wide variables in the 'application' scope. This persists the variable across any view or controller. Does Rails 4 have an equivalent functionality for this type of thing?
The site-wide variable won't typically change often so it doesn't need protecting in any way.
For example, in my situation, I want to store the website's domain name. One for testing and one for live environments. Localhost for development and xxxxxx.com for production.
Any tips or pointers would help. I have Googled this extensively and solutions seem to be far too complicated to achieve what seems to be such a trivial task. What's the best elegant solution for Rails 4?
The simplest, basic and default way is to use the Rails.application.config store.
Rails.application.config.my_config = 'foo'
You can assign a config in your environment:
# application.rb
module MyApp
class Application < Rails::Application
config.my_config = 'foo'
end
end
and read it with
Rails.application.config.my_config
# => 'foo'
This approach works well for very simple applications, but if you want something more advanced there are several gems available.
I'm currently using SimpleConfig. The main advantages are:
per-environment configuration. You can configure default configurations for the application, then override defaults with environment specific configurations
local.rb file for custom overrides
capistrano-like configuration style
it works nicely with the dotenv gem, very useful to avoid storing sensitive credentials in your repo.
This sounds like a perfect example for configuration values stored in config/environments/production.rb and config/environments/development.rb. Just store any value there:
config.my_special_value = 'val'
And access it in your application like this:
Rails.application.config.my_special_value
Always the value of your environment is active.
If you just want to have a „global“ value, store it in your application controller. All your view controllers are derived from your app controller, so you can save any value there as an instance or class variable:
class ApplicationController < ActionController::Base
MY_CONSTANT_VALUE = "foo"
end
class MyViewController < ApplicationController
def index
raise MY_CONSTANT_VALUE.inspect
end
end
You also could implement an helper:
# app/helpers/application_helper.rb
module ApplicationHelper
FOO = "bar"
end
# app/controllers/foo_controller.rb
class FooController < ApplicationController
def index
raise FOO
end
end
I can recommend good method to store variable. I use this on production
Passwords can be stored easier to .env file
like this
#Root dir create file ".env"
PASSWORD=123456
and load password
#Somewhere in app
ENV['PASSWORD'] #=> 123456
it works I hope will help you
You can use gem figaro
write your variables in config/application.yml
HELLO: world
development:
HELLO: developers
production:
HELLO: users
Then you can fetch
ENV["HELLO"]
In rails there is gem named as
gem 'dotenv-rails'
By using it we can assign the variables to system level and used in application.
By using simple steps
First create a simple filed in system level at any place with named extension .env
//in application.rb
require 'dotenv'
Dotenv.load('path-of-your-file.env')
And restart your application
Source
Please got the link for the desscription of dot env gem
I have a rails 3 engine. In initializer it requires a bunch of files from some folder.
In this file user of my engine defines code, business logic, configures engine, etc..
All this data is stored statically in my engine main module (in application attribute)
module MyEngine
class << self
def application
#application ||= MyEngine::Application.new
end
end
end
I want this files to be reloaded on each request in development mode.
(So that the user don't have to reload server to see changes he just made)
Of course I can do something like this instead of initializer
config.to_prepare do
MyEngine.application.clear!
load('some/file')
end
But this way i will have issues (because constants defined in this file won't really be reloaded).
The ideal solution would be to make my whole engine reloadable on each request, but a have not found the way to do it.
It's an old question but I think adding ActiveSupport::Dependencies.explicitly_unloadable_constants += %w[ GemName ] to your development.rb should do the trick.
Have you tried turning reload_plugins on?
# environments/development.rb
config.reload_plugins = true
Its a bit of hack but using require_dependency and just reopening the class might work?
# app/models/project.rb
require_dependency File.join(MyEngine::Engine.root, 'app', 'models', 'project')
class Project
end
For those who are working on Engine views or I18n translations only: Those parts are autoreloaded by default, no need to restart the server!