1.override,final的使用，兩者都是針對虛函數，也就是說要有virtual關鍵字

#include <iostream>

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//C++中的final和override主要是針對虛函數

//加了final表示拒絕重寫，這是為了使某些情況下，拒絕接口的重寫

//override,聲明重寫父類的方法，前提是要有virtual關鍵字修飾函數。

//當父類沒有接口，會提示錯誤

class ye

{

public:

??? //final修飾的函數必須是虛函數,通過這種方式避免重寫了一些老的接口

??? virtual void print() final //加了final表示虛函數無法重寫了

??? {

??????? std::cout << "爺爺\n";

??? }

??? virtual void run()

??? {

??????? std::cout << "爺爺run\n";

??? }

};

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class ba :public ye

{

public:

??? void run() override

??? {

??????? std::cout << "爸爸run\n";

??? }

};

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void main()

{

??? ba ba1;

??? ba1.run();? //結果是：爸爸run

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??? std::cin.get();

}

2.RTTI 實時類類型檢測

#include <iostream>

//rtti,實時類類型檢測

//typeid,dynamic_cat必須依賴于虛函數表

//類型不匹配轉換失敗，返回為空，類型安全

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//成員變量的覆蓋

//虛函數有虛函數表確定數據類型

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class A

{

public:

??? int num;

??? static int data;

??? virtual void run()

??? {

??????? std::cout << "A run \n";

??? }

};

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//對A中的靜態變量進行初始化

int A::data = 1;

class B :public A

{

public:

??? int num = 0;

??? static int data;

??? void run()

??? {

??????? std::cout << "B run\n";

??? }

??? void test()

??? {

??????? std::cout << num << "\n";

??????? std::cout << "B test\n";

??? }

};

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int B::data = 2;

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void main()

{

??? A a1;

??? B b1;

??? A *p1 = &a1;

??? A *p2 = &b1;

??? B *p3(nullptr);

??? //p3 = static_cast<B *>(p1);//直接賦地址，不安全，與虛函數無關

??? p3 = reinterpret_cast<B *>(p2);

??? std::cout << p3 << "\n";

??? p3->test();

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??? std::cin.get();

??? //此次運行結果：

??? //008FFE70

??? //0

??? //B test

}

3.C函數指針復習

#include <stdlib.h>

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int add(int a,int b)

{

??? return a + b;

}

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void run()

{

??? printf("\nrun");

}

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void main()

{

??? int(*p)(int, int) = add;//指向add的函數指針

??? void(*p1)() = run;//指向run的函數指針

??? printf("%d\n",p(1,2));

??? printf("%d\n",(*p)(1,2)); //*p編譯器自動將*p解釋為p

??? printf("%d\n",(******p)(1,2));//*p編譯器自動將*p解釋為p

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??? printf("%d\n", (&(**p))(1, 2)); //&沒有*不可以執行，超過兩個地址就不可以

??? //&p不能，

??? //printf("%d\n", (&(p))(1, 2));

??? printf("%p,%p,%p", &p, *p, p);

??? printf("\n%p,%p,%p", &p1, *p1, p1);

??? //取地址，就是CPU即將調用函數執行

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??? getchar();

}

運行結果：

4.CPP函數指針

#include <iostream>

#include <stdlib.h>

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void add(int a,int b)

{

??? std::cout << a + b << std::endl;

}

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void main()

{

??? void(*p)(int, int) = add;

??? p(1, 2);

??? (*p)(1,2); //函數指針，會被當做指針來處理，*p與p效果一樣

??? (*************p)(1,2);//函數指針，會被當做指針來處理，*p與p效果一樣

??? (*&p)(1,2);

??? (*******&p)(1,2);

??? std::cout << (void *)p << "? " << (void *)(*p) << std::endl;

??? std::cout << typeid(p).name() << std::endl;

??? std::cout << typeid(*p).name() << std::endl;

??? std::cout << typeid(&p).name() << std::endl;

??? std::cout << typeid(*&p).name() << std::endl;

??? //C++編譯器會自動將*p處理為p

??? std::cin.get();

}

運行結果：

5.類成員函數指針數組

#include <iostream>

#include <stdio.h>

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//類成員函數指針，類成員函數指針數組，類成員二級函數指針

class com

{

private:

??? int a;

??? int b;

public:

??? com(int x, int y) :a(x), b(y)

??? {

??? }

??? int? jia(int a, int b)

??? {

??????? return a + b;

??? }

??? int? jian(int a, int b)

??? {

??????? return a - b;

??? }

??? int? cheng(int a, int b)

??? {

??????? return a * b;

??? }

??? int? chu(int a, int b)

??? {

??????? return a / b;

??? }

};

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void main()

{

??? com com1(100, 20);

??? auto fun1 = &com::jia;

??? int(com::*p)(int, int) = &com::jia;? //注意這里要加上對象名

??? std::cout << (com1.*p)(10, 20) << std::endl;//引用對象，類成員函數指針

??? std::cout << typeid(p).name() << std::endl;

??? std::cout << typeid(fun1).name() << std::endl;

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??? std::cin.get();

}

5.CPP函數指針數組

#include <iostream>

#include <stdio.h>

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//類成員函數指針，類成員函數指針數組，類成員二級函數指針

class com

{

private:

??? int a;

??? int b;

public:

??? com(int x, int y) :a(x), b(y)

??? {

??? }

??? int? jia(int a, int b)

??? {

??????? return a + b;

??? }

??? int? jian(int a, int b)

??? {

??????? return a - b;

??? }

??? int? cheng(int a, int b)

??? {

??????? return a * b;

??? }

??? int? chu(int a, int b)

??? {

??????? return a / b;

??? }

};

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typedef int(com::*P)(int, int);//為函數指針定義別名p

void main()

{

??? com com1(100, 200);

??? //下面這種方式也是沒有錯的

??? //P fun1[4] = { &com::jia, &com::jian, &com::cheng,&com::chu };

??? //類成員函數指針數組

??? int(com::*fun1[4])(int, int) = { &com::jia, &com::jian, &com::cheng, &com::chu };

??? for (int i = 0; i < 4; i++)

??? {

??????? std::cout << (com1.*fun1[i])(10, 20) << std::endl;

??? }

??? int(com::**funp)(int, int) = fun1;//指向類成員函數指針的指針

??? for (; funp < fun1 + 4;funp++)

??? {

??????? std::cout << (com1.**funp)(10, 20) << std::endl;

??????? printf("%p",*funp);

??? }

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??? for (int i = 0; i < 4;i++)

??? {

??????? auto func = fun1[i];

??????? std::cout << typeid(func).name() << std::endl;

??????? printf("%p", func);

??? }

??? std::cin.get();

}

運行結果：

6.高級new對象

#include<iostream>

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class myclass

{

public:

??? myclass()

??? {

??????? std::cout << "創建\n";

??? }

??? ~myclass()

??? {

??????? std::cout << "銷毀\n";

??? }

};

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void main()

{

??? char *pcathe = new char[1024];

??? char *pcatheend = pcathe + 1024;

??? std::cout << (void*)pcathe << "?? " << (void*)pcatheend << std::endl;

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??? myclass *p = new(pcathe)myclass[10];//限定區域分配內存，覆蓋模式

??? std::cout << p << std::endl;

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??? //delete[] p;一般不需要delete.自動覆蓋

??? std::cout << p << std::endl;

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??? p = new(pcathe)myclass[10];

??? std::cout << p << std::endl;

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??? //delete[] p;//只能釋放一次

??? std::cout << p << std::endl;

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??? /*

??? myclass *pclass = new? myclass[10];

??? std::cout << pclass <<std::endl;

??? delete []pclass;

??? pclass = NULL;

??? std::cout << pclass <<std::endl;

??? pclass = new?myclass[10];

??? std::cout << pclass <<std::endl;

??? delete [] pclass;

??? std::cout << pclass <<std::endl;

??? */

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??? std::cin.get();

}

總結

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