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Ruby dot and double colon operators

Ruby . and :: operators

In Ruby you call a module method by preceding its name with the module's name and a period and you refer a constant using the module name and two colons.

The :: is a unary operator and is used to access (anywhere outside the class or module) constants, instance methods and class methods defined within a class or module.

Note: In Ruby, classes and methods may be considered constants too.

You must prefix the :: Const_name with an expression that returns the appropriate class or module object. If no prefix expression is used, the main Object class is used by default.

Here is an example :

X = 0        # constant defined on main Object class
module Calculate
  X = 0
  ::X = 10    # set global count to 10
  X = 20     # set local count to 20
end
puts X       # this is the global constant
puts Calculate::X  # this is the local "Calculate" constant

Output:

abc.rb:4: warning: already initialized constant X
abc.rb:1: warning: previous definition of X was here
abc.rb:5: warning: already initialized constant Calculate::X
abc.rb:3: warning: previous definition of X was here
10
20

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