[Tang Laoshi] C -- encapsulation: member variables and access modifiers

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Class is a template for an object

Used to abstract real objects

 

Object is an instance of a class

Used to represent a real object individual

 

Class is a custom variable

Instantiate class objects

Is declaring variables

Today we will study in the future

Characteristics of the object

Member variables

 

【 Member variables 】

         Object oriented programming idea , Simply put, it is abstracted with program language （ Describe ） A real object appears . Now we know that classes are used to describe objects , Objects are instantiated from classes . Specific The characteristics and behavior of objects stay Class representation Mainly through ： Member variables and member methods Embodied .

Member variables

↓↓↓↓

Declare variables in classes

↓↓↓↓

Write in a class statement block

 

Basic rules for member variables

1. Declared in a class statement block

2. Whether the assignment is determined according to the requirements

3. It is used to describe the characteristics of objects

4. It can be of any kind

5. There is no limit to the quantity

         First of all, I want to emphasize a point , Class is also a variable type , It's just a custom variable type . It and the structure 、 Enumerations are very similar , It is a variable rule that we can name and define ourselves . So, in the above example, in Person Owned by Person Variables are fully allowed ！ You need to understand its concept with object-oriented thinking , Just like you are human , You also have to have a human girlfriend ~

How to use these member variables ？

First we must learn the access modifier

↓↓↓↓

 

【 Access modifier 】
 

Access modifier

Current decision

Member variables

Member method

Access rights of

keyword

public—— public

private—— private

protected—— Protect

 

The access modifier is written before the member variable declaration

Determines the access rights of member variables

 

1. Public member variables , You can point it out

2. Private member variables , Can only be used inside a class

3. Protected member variables , When we inherit

public

Public member variables

Inside and outside the class

at will Access modification

private

Private member variables

Can only Inside the class

at will Access modification

protected

Explain when inheriting

When declaring member variables

Do not write access modifiers

The default is private

【 Use member variables 】

 

 

 

【 summary 】
 

Access modifier

Determine access to member variables

public—— public

private—— private

Member variables

Describe the characteristics

Class

The assignment is arbitrary

Any type

Any number

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