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