Module vs class in ruby programming language
on Ruby
Modules are about providing methods that you can use across multiple classes - think about them as “libraries” (as you would see in a Rails app). Classes are about objects; modules are about functions. Class is mainly different from Module by 3 main methods: new, allocate, superclass.
The table below show you the different between them.
| Class | Module | |
|---|---|---|
| instantiation | can be instantiated | can not be instantiated |
| usage | object creation | mixin facility. provide a namespace. |
| superclass | module | object |
| methods | class methods and instance methods | module methods and instance methods |
| inheritance | inherits behaviour and can be base for inheritance | No inheritance |
| inclusion | cannot be included | can be included in classes and modules by using the include command (includes all instance methods as instance methods in a class/module) |
| extension | can not extend with extend command (only with inheritance) | module can extend instance by using extend command (extends given instance with singleton methods from module) |
Example codes
module A
class B
def initialize
@ins_var = 1
end
end
end
a = A.new # undefined method new for A:Module
a = A::B.new
puts a.ins_var # 1