How to Store Site-Wide Variables in Rails 4

Where can I store site-wide variables in 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.

Where store or implement global variables ($) in Rails?

Rails does it that way:
https://guides.rubyonrails.org/configuring.html#custom-configuration

In config/environments/production.rb:

config.myGlobalVariable = 'blabla1'

In config/environments/development.rb:

config.myGlobalVariable = 'blabla2'

then use this Anywhere:

Rails.configuration.myGlobalVariable

Permanent variable in Rails

Ok, so here's what I did. Instead of just putting the value to an initializer, I've made there a simple class that handles it. The variable itself is stored in a predefined file. Besides of reading the file upon the initialization, the class updates file when the value is changed, and also re-read the file periodically to maintain consistency across workers. I've also put there some basic JSON handling and backup functionality to make life easier.

For anyone interested, here's the important code:

class Pomegranate

  def initialize
    @delay = 30.minutes
    @path = "db/pomegranate.json"
    @valid = Time.now - 1
    validate
  end

  def get(*p)
    validate
    p.inject(@data) {|object,key| object[key] if object}
  end

  def set(*p, q, v)
    hash = p.inject(@data) {|object,key| object[key]||={}}
    hash[q] = v
  end

  def save
    @valid = Time.now + @delay
    File.open(@path,"w") {|f| f.write(@data.to_json)}
  end

  private

  def validate
    if @valid < Time.now
      @data = ActiveSupport::JSON.decode(File.read(@path)) rescue {}
      @valid = Time.now + @delay
      @valid = Time.now - 1 if @data.empty?
    end
  end

end

$pom = Pomegranate.new

Global mutable variable in Ruby on Rails 5

This can be an answer for you:

1. Create a model for site information probably you already have.
2. Add two fields called targe and progress.
3. If you calculate progress programatically then no need to add field.
4. Then make view where they can update target and progress and write logic to update that field only.
   Programmatically there is not a good idea other than this. I think.

Ruby on Rails - Global Variable?

A global variable doesn't fit your need. It doesn't spread across all the Ruby processes. If your web server spawns 5 ruby processes to handle 5 request at the same time, the variable defined in the first process won't be visible to the others.

There are other solutions available. You can use a database and store the flag/information on the database. Otherwise, you can use a file and store the value in the file.
The best solution would be an in-memory shared data source, such as memcached or Redis.

safe and performing way to save site wide variable

It depends whether it has to be perfectly accurate. Assuming not, you can store it in memcached and sync to the database occasionally. If memcached crashes, it expires (shouldn't happen if configured properly), you have to shutdown, etc., reload it from the database on startup.

You could also look at membase. I haven't tried it, but to simplify, it's a distributed memcached server that automatically persists to disk.

For better performance and accuracy, you could look at a sharded approach.

Setting a site-wide variable for text-field max length - Rails

Create an entry in config/application.rb:

config.header_max_length = 50

And use this while creating forms:

<%= f.text_field :title, nil, maxlength: Rails.application.config.header_max_length %>

To make it more DRY you could create a helper method for a custom text_field_with_maxlength or create a custom FormBuilder.

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