What does :: do in Foo::Bar?
I thought it was related to encapsulation (private, protected), but it's not that when I looked at the definition.
The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or module.
Then ::: doesn't have to be there, does it? It doesn't restrict access, but it can be accessed anywhere by just filming ::, but why is this there?
::: is an operator related to namespace. It is used to access the item in the module or class.
For example,
module SomeModule
module InnerModule
class MyClass
CONSTANT = 4
end
end
end
When writing these codes, to access CONSTANT outside SomeModule
SomeModule::InnerModule::MyClass::CONSTANT.
You have to share it.
The reason for writing ::: is not to restrict access, but to "prevent name conflicts between methods and classes."
Considering the case of joint development, there is a high possibility that the variable will have the same name. But should we check what other people are using? This is a very inefficient way. So you can write code freely on different namespaces to avoid conflicts.
MR_COUNT = 0 #constant (1) defined in the main object class
module Foo
MR_COUNT = 0 # Constant (2) as defined by Foo
::MR_COUNT = 1 # Set (1) to 1
MR_COUNT = 2 #(2) set to 2
end
puts MR_COUNT # (1)
puts Foo::MR_COUNT # (2)
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