ActiveRecord::Base

rubyonrails-talk
1

Hello all,

      What is significance of :: in ActiveRecord::Base.

What is difference between ::String.new and String.new

Thank you, Praveen

2

::String means explicit root namespace.

So if you have something like module MyNamespace class String … end end

MyNamespace::String will be your own class, while ::String will still be the original string class defined by Ruby. If you just type String, it’ll find the closest matching namespace, so if you call String.new from within MyNamespace, it’ll return MyNamespace::String, while if you call String.new from outside MyNamespace, it’ll call the default Ruby string. Writing ::String means you explicitly want the default Ruby string, even if you call it from inside MyNamespace.

3

Good question!

Using :: you have access to the class inside the module. Module can nest another modules and so on. :: its a namespace resolution operator.

Call ::String.new inside some module back you to top-level namespace (outside the module)

Here is examples

class String def initialize    puts "im string outside module" end end

module ActiveRecord   module AnotherModule   end

  class String    def initialize      puts "im string inside module"    end   end

  class Base    def initialize     ::String.new     String.new    end   end end

Here are results from IRB:

1.9.3-p392 :021 > ActiveRecord::Base.new im string outside module im string inside module => #<ActiveRecord::Base:0xa024fb8> 1.9.3-p392 :022 > ActiveRecord::String.new im string inside module => #<ActiveRecord::String:0xa023168>