Effective C++条款33 避免遮掩继承而来的名字

而来的名字"/>

Effective C++条款33 避免遮掩继承而来的名字

名称遮掩

int x = 20;void someFunc()
{double x = 10.0; std::cout << x;
]

如上操作，函数打印结果是10.0还是20呢？是10.0。因为代码访问顺序是这样的，当需要变量x，现在someFun()函数里找，找不到x，再全局找x。本例：double x遮掩了int x

继承中的名称遮掩

• Derived类的调用作用域顺序

class Base
{
public:virtual void mf2();
};class Derived :public Base
{
public:void mf4(){fm2(); //调用基类中的fm2}
};

mf4()再函数内查找fm2----在Derived类查找fm2()------ 在Base类查找mf2()

• 隐藏基类函数的情形

#include <iostream>
class Base
{
private:int x;
public:virtual void mf1() = 0;virtual void mf1(int);virtual void mf2();void mf3();void mf3(double);
};class Derived :public Base
{
public:virtual void mf1();void mf3();void mf4();
};
int main()
{Derived d;int x = 10;d.mf1();  //正确d.mf1(x); //错误，Base::fm1(int)被隐藏了d.mf2();  //正确d.mf3();  //正确d.mf3(x); //错误，Base::mf3(double)被隐藏了return 0;
}

• 可在Derived类加上using Base, 让Base类的作用函数对Derived类可见，不再隐藏

class Derived :public Base
{
public:using Base::mf1;using Base::mf3; //取消隐藏virtual void mf1();void mf3();void mf4();
};

• 也可以通过在Derived类调用Base类的函数--避免隐藏Basse类的函数

#include <iostream>
class Base
{
public:void mf1(int a){printf("====%d\n ",a );};
};class Derived :public Base
{
public:void mf1(){Base::mf1(10);};};
int main()
{Derived d;  d.mf1();  //正确return 0;
}