Rails: Run initializer before creating classes

问题

Basically I have an initializer class at RAILS_ROOT/config/initialiers/app_constant.rb to make everything easy to control.

class AppConstant
  APIURL = 'http://path.to.api'
end

And in the RAILS_ROOT/model/user.rb, I have the settings:

class User < ActiveResource::Base
  self.site = AppConstant::APIURL
end

And when run rails s, I got the following error

<class:User>: uninitialized constant User::AppConstant::APIURL

I know that the problem is because Rails run Initializers after creating the Classes. Is there any way to make some Initializers run before Rails setup it classes?

---

Finally this problem is solved by adding require "#{Rails.root}\conf\initializers\app_constant.rb" to the application.rb which is loaded right before Rails loads models.

回答1:

To have code run before Rails itself is loaded, put it above require 'rails/all' in config/application.rb.

回答2:

Another solution would be to wrap the constant in a method so it is not evaluated when the class is loaded, but only later when the method is called:

def self.site
  AppConstant::APIURL
end

If it needs to be settable as well:

def self.site=(url)
  @site = url
end

def self.site
  @site ||= AppConstant::APIURL
end

来源：https://stackoverflow.com/questions/10683666/rails-run-initializer-before-creating-classes