Operators in Ruby

Question

What is the difference in dot operator, colon operator and scope resolution operator in Ruby?

Where and why are they used?

Answer 1

The dot operator separates an object and a method belonging to that object, for example "Hello".reverse or

def self.my_singleton_method
end

This single colon isn't really an operator. It can be used in ruby 1.8 instead of then in an if or case/when statement. In ruby 1.9 it can be used in hash literals, e.g. {A : 65}. It precedes an identifier to form a Symbol, e.g. :red, and it's used in the ternary condition operator ?:.

The double colon operator is the scope resolution operator. It specifies in which class or module you reference a constant. Note that classes and modules are themselves constants.

module MyModule
  class Object
  end

  p Object           # prints "MyModule::Object"
  p ::Object         # prints "Object"
end

Preceding a constant with :: means that you take it from the outer, or global, scope.

Answer 2

The . is used for method calls

The : is used to define symbols

The @ @@ $ is used to denote a scope