Ruby journey (6) modules and multi-inheritance of Classes

In addition to class, Ruby also supports module, which has two functions:
1. namespace used as a group method and constant to prevent name conflicts
2. Mixin classes can be mixed in. Instances of Mixin module classes have module methods.

If different classes are mixed into the same module, they can have the same function without inheriting a parent class.

You can include a module to implement multiple inheritance in C ++.

Module circularmodule
Pi =   3.1415926
Def Calculate (diamiter)
Return Diamiter * Pi
End
End

Class Circular
Include circularmodule
End

C = Circular. New
Puts C. Calculate ( 5 ) # Output 15.707963

As you can see, after using include to include a module, this class will contain the methods and constants in the module. The method uses the object name. method name, and the constant uses the Class Name: constant.