Rails Include Module on Condition

I'm trying to include a module only when a condition is met.

module PremiumServer
  def is_premium
    开发者_如何学Ctrue
  end
end

class Server
  include Mongoid::Document
  include PremiumServer if self.premium
  field :premium, :type => Boolean, :default => false
end

This isn't working, and I can't figure out why. Can someone please tell me how I'm supposed to include modules based upon a condition being met, like above?

Thanks!

EDIT:

I found the answer to my problem here: Mongoid and carrierwave

However, I'm awarding the question to the top answer as it is probably the more useful way.

includes happen on the class level. Your premium attribute is at instance level.

There are ways to do the include on per instance level, but I would not recommend them.

Here you are better of using inheritance

class Server; .. ; end
class PremiumServer < Server; ..; end

Or, in your case, if the only method is is_premium add it to the Server class and have it return the premium variable

def is_premium
  self.premium
end

oh, and you should use "question" method in ruby... Although Mongoid provides these for boolean values.

def premium?
  self.premium
end

Use class inheritance and the scope mechanism of Mongoid:

class Server
  include Mongoid::Document
  field :premium, type: Boolean, default: false
  # ... basic server methods
end

class PremiumServer < Server
  default_scope :premium_servers, where(premium: true)
  # ... additional premium server methods
end

p_server = PremiumServer.first
p_server.<access to PremiumServer methods>

The default_scope will be used every time you do a query on PremiumServer, you do not need to call .premium_servers manually.

That is "conditional based" in another way - in a mongoid way.

Further information:

• Scopes: http://mongoid.org/docs/querying/scopes.html
• Inheritance: http://mongoid.org/docs/documents/inheritance.html