Class inheritance python-CodePudding

In the case creating a model, for example class Student(models.Model)
name=models.charfield(),roll=models.integerfield()

similarly, In the case creating a form, class newform(forms.Form) name=forms.charfield(),roll=forms.integerfield()

similarly, In the case creating a serializer, class serial(serializers.Serializer) name=serializers.charfield(),roll=serializers.integerfield()

I understood that in each classes,a base class is inherited but i am confused that if different objects of different classes are created inside a class in each scenario then what is the meaning of inheriting models.model, forms.Form,serializers.Serializer what these inherited classes do?

CodePudding user response：

Django uses inheritance as well as object composition which are techniques of OOP for reusability.

Let us take your first class as example (I have only kept one field for simplicity):

Student(models.Model):
   name = models.CharField(max_length=100)

Inheritance:

The first line Student(model.Model): does inheritance by inheriting from Model class using which you are getting methods like save(), delete(), clean_fields e.t.c. Now your Student class can reuse those methods.

Composition

The second line name = models.CharField(max_length=100) does object composition by creating object namely name of class CharField using which you get methods like check, get_internal_type e.t.c.

All of those Inbuilt classes (Model, CharField e.t.c) are defined in file namely models.py so when you do models.Model you are getting Model class from file models.py and models.CharField gives you CharField class from same file.

CodePudding user response：

By inheriting from other classes, you have access to their methods;

Class A(object): 
    def _print(self): 
        print('Class A') 

Class B(A): 
    def other_print(self): 
        print('Class B')

if __name__ == "__main__":
    a, b = A(), B() 

    a._print()

    b._print()
    b.other_print()

When inheriting from model, forms, etc... You inherit from an object that is already integrated in the framework and thus has specific methods to work with the framework. For example the model will be registered to the database, the form 'knows' how to render properly, etc...

When you inherit from these classes, you already have an pre-built object with all these methods.