C++ 第三章 纯虚函数Virtual报错

Virtual 后的函数=0则为纯虚函数

#include 

using namespace std;

class FA {
public:
	void Func1() {
		printf("FA::Func1 n ");
	}
	//void Func1(int a) {

	//}
	//void Func1(int a, int b) {

	//}
	//void Func1(int a, int b, int c) {

	//}
};



class FB:public FA{
public:
	void Func1(){
		printf("FB::Func1 n ");
	}
};

class IInterface {
public:
	virtual void Init() = 0;//带0则为纯虚函数
	virtual void Distroy() = 0;
};

class FNewObject:public IInterface{
public:
	FNewObject () {}

};



int main() {

	//FA::Func1();

	//FA::Func1(1);

	//FA::Func1(1, 2);

	//FA::Func1(1, 2, 3);
	//FB A;
	//A.Func1();

	//FA* p = &A;
	//p->Func1(); 
	//A.Func1(1, 2);
	//A.Func1(1, 2, 3);
	FNewObject Obj;
	return 0;
}

上面的代码的Obj实例化会报错，原因就在于带有纯虚函数的类的派生类
必须要重写一遍纯虚函数
如下则不会报错(下面没写实现，记得加实现)：

#include 

using namespace std;

class FA {
public:
	void Func1() {
		printf("FA::Func1 n ");
	}
	//void Func1(int a) {

	//}
	//void Func1(int a, int b) {

	//}
	//void Func1(int a, int b, int c) {

	//}
};



class FB:public FA{
public:
	void Func1(){
		printf("FB::Func1 n ");
	}
};

class IInterface {
public:
	virtual void Init() = 0;//带0则为纯虚函数
	virtual void Distroy() = 0;
};

class FNewObject:public IInterface{
public:
	FNewObject () {}
	virtual void Init();//带0则为纯虚函数
	virtual void Distroy();
};



int main() {

	//FA::Func1();

	//FA::Func1(1);

	//FA::Func1(1, 2);

	//FA::Func1(1, 2, 3);
	//FB A;
	//A.Func1();

	//FA* p = &A;
	//p->Func1(); 
	//A.Func1(1, 2);
	//A.Func1(1, 2, 3);
	FNewObject Obj;
	return 0;
}