对于struct和class的认识

Posted 2020-06-14

之前一直以为c++中有class的原因是c中的struct不能有构造函数，析构函数，继承等功能，没想到struct也可以实现这些功能。

只不过class中默认的关键字是private，而struct中默认的关键字是public。

以一个例子来说明用struct实现类的一些功能。

eg:

#include <iostream>
using namespace std;
enum BREED {GOLDEN,CAIRN,DANDIE,SHETLAND,DOBERMAN,LAB};//BREED是一种数据类型了，其值可以是括号里的任意一个，第一个默认为0

struct Mammal
{
protected:
int itsAge;
int itsWeight;
public:
Mammal() :itsAge(2), itsWeight(5){}
~Mammal(){}
int GetAge() const { return itsAge; }
void SetAge(int age){ itsAge = age; }
int GetWeight() const { return itsWeight; }
void SetWeight(int weight){ itsWeight = weight; }

void Speak() const { cout << "\n Mammal sound! \n"; }
void Sleep() const { cout << "\n Shhh.I‘m sleeping"; }
};

struct Dog :public Mammal
{
private:
BREED itsBreed;
public:
Dog() :itsBreed(GOLDEN){}
~Dog(){}
BREED getBreed() const { return itsBreed; }
void SetBreed(BREED breed){ itsBreed = breed; }
void WagTail() const { cout << "Tail wagging...\n"; }
void BegForFood() const { cout << "Begging for food...\n"; }
};

int main()
{
Dog fido;
fido.Speak();
fido.WagTail();
cout << "Fido is " << fido.GetAge() << "years old \n";
return 0;
}

 

输出为：Mammal sound!

Tail wagging...

Fido is 2years old