C++ 从派生类访问基类公共成员
是否可以从程序中某些其他位置的派生类实例访问基类公共成员C++ 从派生类访问基类公共成员,c++,inheritance,C++,Inheritance,是否可以从程序中某些其他位置的派生类实例访问基类公共成员 class base { public: int x; base(int xx){ x = xx; } }; class derived : base { public: derived(int xx) : base(xx){ } }; class main { public: derived * myDerived; void m1(){
class base {
public:
int x;
base(int xx){
x = xx;
}
};
class derived : base {
public:
derived(int xx) : base(xx){
}
};
class main {
public:
derived * myDerived;
void m1(){
myDerived = new derived(5);
m2(myDerived);
}
void m2(derived * myDerived){
printf("%i", myDerived->x);
}
};
在上面的代码之后,我得到了以下错误
`error: 'int base::x' is inaccessible`
您可以从基类私下继承。您通常需要的是公共继承:
class derived : public base
class derived : public base
^^^^^^
class derived : public base {
...
};
这是关于私有继承的问题。问题是您在这里不小心使用了私有继承
class derived : base {
这使得派生类中的所有基类成员都是私有的
将此更改为
class derived : public base {
它将按预期工作。那么,您应该公开地从
base
继承
class derived : public base {
public:
derived(int xx) : base(xx){
}
};
私有继承用于非常特殊的情况,例如当两个类之间存在
has-a
关系,但还需要重写基类的成员时。从类外部,只能访问公共基类的公共成员;当您使用class
关键字定义类时,默认情况下继承是私有的
要使其可访问,您需要公共继承:
class derived : public base
class derived : public base
^^^^^^
class derived : public base {
...
};
尝试:
使用公共继承:
class derived : public base
class derived : public base
^^^^^^
class derived : public base {
...
};
或
将x设为私有而不是公共,并使用以下代码:
class Base {
int x;
public:
Base (int xx) {
x = xx;
}
void display() {
cout << "x = " << x << endl;
}
};
class Derived : public Base {
public:
Derived (int xx) : Base (xx) {
}
};
int main() {
Derived d1(2);
Derived *d = new Derived(10);
d->display();
d1.display();
return 0;
}
类基{
int x;
公众:
基地(int xx){
x=xx;
}
无效显示(){
库特