On insect classes and objects

1. Classes and objects
   1. Preliminary understanding of process oriented and object-oriented
   2. Class introduction
   3. The definition of a class
      1. Two ways to define classes
   4. Class access qualifier and encapsulation
      1. Access qualifier
      2. Interview questions ：c++ in struct and class What's the difference
      3. Interview questions ： Three characteristics of object-oriented encapsulation Inherit polymorphic

Classes and objects

Preliminary understanding of process oriented and object-oriented

C Language is == Process oriented == Of ,== Focus on == Yes. == The process ==, Analyze the steps to solve the problem , Solve the problem step by step through the function call .
C++ yes == Based on object-oriented == Of ,== Focus on == Yes. == object ==, Split a thing into different objects , It depends on the interaction between objects

Class introduction

==C In language , Only variables can be defined in the structure , stay C++ in , Not only can variables be defined in a structure , You can also define functions ==

== such as c Define a stack in language ==

== and c++ Class is introduced in What is class Class is to define a new type ==

== Class consists of two parts ：1. Member variables （ attribute ）2. Member functions （ Behavior ）==

==c++ Medium struct compatible c All uses of , meanwhile c++ Zhongba struct Upgrade to class ==

The definition of the above class ,== stay C++ I prefer to use class Instead of ==

This is why the definition of class in school is not struct, It is class

The definition of a class

class A{ // The class body ： It consists of member functions and member variables };  // Like the structure, don't forget the semicolon 

==class== Define the of the class == keyword ==,==A Is the name of the class ==,=={} Is the body of the class ==, Be careful == Class definition ends with a semicolon ==.
The elements in the class are called == Class members ==： Class == data == be called == Attributes of a class == perhaps == Member variables ==; Class == function == be called == Class method == perhaps == Member functions ==.

Two ways to define classes

Declarations and definitions are all placed in the class body , We need to pay attention to ： If a member function is defined in a class , The compiler may treat it as an inline function
The reason is .

The statement is placed in .h In file , The definition of a class is placed in .cpp In file

Class access qualifier and encapsulation

Access qualifier

C++ The way to achieve encapsulation ：== Use classes to combine the properties and methods of objects , Make the object more perfect , Selectively provide its interface to external users through access rights ==

== Access qualifier description ==

1. public Decorated members can be accessed directly outside the class
2. protected and private Decorated members cannot be directly accessed outside the class ( here protected and private It's similar )
3. The access scope is from == The position where the access qualifier appears begins until the next access qualifier appears ==
4. class Of == The default access is private==,==struct by public==( because struct To be compatible with C)

Interview questions ：c++ in struct and class What's the difference

C++ Compatibility required C Language , therefore C++ in struct It can be used as a structure . in addition C++ in struct It can also be used to define classes . and class Yes, the definition class is the same , The difference is that ==struct The default access method for members is public,class Yes, the default access method for members is private.==

Interview questions ： Three characteristics of object-oriented encapsulation Inherit polymorphic

In fact, there are more than three characteristics such as == abstract Reflection ==

In the class and object phase , We only study == Class encapsulation features ==, What is encapsulation ？

== encapsulation ==： Organically combine data and methods of operating data , Hide object properties and implementation details , Only expose interfaces to interact with objects .

== Data and methods are encapsulated in classes , Manage , I want to define your access as shared , What you don't want to access is defined as private or protected ==

== Encapsulation is essentially management ==： How do we manage the terracotta warriors and horses ？ For example, if you don't care about anything , The terracotta warriors and horses were destroyed at will . So we first built a house to encapsulate the terracotta warriors and horses . But our purpose is completely encapsulated , Don't let others see . So we opened the ticket channel , You can buy tickets and visit under a reasonable supervision mechanism . Class is the same , We use class data and methods encapsulated in .
What you don't want others to see , We use protected/private Encapsulate members . Open some common member functions for reasonable access to members . So encapsulation is essentially a kind of management .