在面试中常常会有面试官问道，c++的多态的实现机制。那么，多态到底该如何实现呢？
多态的简单介绍
一般来说，多态分为两种， 静态多态和 动态多态。静态多态也称编译时多态，主要包括 模板和 重载。而动态多态则是通过类的继承和虚函数来实现，当基类和子类拥有同名同参同返回的方法，且该方法声明为虚方法，当基类对象，指针，引用指向的是派生类的对象的时候，基类对象，指针，引用在调用基类的虚函数，实际上调用的是派生类函数。这就是动态多态。
静态多态的实现
静态多态靠编译器来实现，简单来说就是编译器对原来的函数名进行修饰，在c语言中，函数无法重载，是因为，c编译器在修饰函数时，只是简单的在函数名前加上下划线”_” ,不过从gcc编译器编译之后发现函数名并不会发生变化。而c++编译器不同，它根据函数参数的类型，个数来对函数名进行修饰，这就使得函数可以重载，同理，模板也是可以实现的，针对不同类型的实参来产生对应的特化的函数，通过增加修饰，使得不同的类型参数的函数得以区分。
以下段程序为例
#include
using namespace std;
template
int fun(T1 t1, T2 t2){}
int foofun(){}
int foofun(int){}
int foofun(int , float){}
int foofun(int , float ,double){}
int main(int argc, char *argv[])
{
fun(1, 2);
fun(1, 1.1);
foofun();
foofun(1);
foofun(1, 1.1);
foofun(1, 1.1, 1.11);
return 0;
}
经过编译之后：
只选取main函数部分来看：
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:7d7abeb1-35fc-42ff-9113-0b40cd21ade8
[En]
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:6bf7b908-0996-41a8-8755-16f1ed91294d
动态多态的实现
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:1efbe4e3-e030-42d8-a96a-3be4e1590151
[En]
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:3bf7538b-ea89-4d1d-ae41-90ee31062a80
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:1cb5ff57-dcde-43b4-ac0e-fc91bd489bd0
[En]
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:04c09b5d-a576-4266-bf93-41253a259fc4
以下段程序为例：
#include
using namespace std;
class Base
{
public:
virtual void fun()
{
cout << "this is base fun" << endl;
}
};
class Derived : public Base
{
public:
void fun()
{
cout << "this is Derived fun" << endl;
}
};
int main(int argc, char *argv[])
{
Base b1;
Derived d1;
Base *pb = &d1;
Derived *pd = (Derived *)&b1;
b1.fun();
pd->fun();
d1.fun();
pb->fun();
return 0;
}
运行结果如下：
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:2ae85ff8-5be4-4bd2-863d-af3f2bfad9ce
[En]
[TencentCloudSDKException] code:FailedOperation.ServiceIsolate message:service is stopped due to arrears, please recharge your account in Tencent Cloud requestId:f6e4c0a1-0f5a-4f5b-a46b-01dff5f84eb9
Original: https://www.cnblogs.com/0x12345678/p/5677598.html
Author: Hackergin
Title: c++多态的实现
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