Question

您好我试图使用继承调用来自不同类的对象成员，但编译器似乎抱怨。有替代方案吗？

我得到的错误是错误C2228：左边的＆＃39; .func＆＃39;必须有class / struct / union

class test
{
public: 
    void func()
    { 
        cout<<"test print"<<endl; // actually performing a complicated algorithm here
    }
};

class demo :public test
{
public: 
    test obj1;
    obj1.func();
};

void main()
{
    demo::obj1.func();// getting an error here
}

Answer 1

有一些问题：

// This part is ok (assuming proper header/using)
class test
{
public: 
    void func(){ 
        cout<<"test print"<<endl; // actually performing a complicated algorithm here
    }
};

// You have demo inheriting from test. I don't think you want that
//class demo :public test
class demo
{
public: 
    test obj1;       // Ok
    // obj1.func();  // Not ok. You can't call a function in a class definition
};

void main()
{
    // There are no static functions. You need to create an object
    //demo::obj1.func();// getting an error here

    demo myObject;
    myObject.obj1.func();
}

或者，如果你想使用继承：

// This part is ok (assuming proper header/using)
class test
{
public: 
    void func(){ 
        cout<<"test print"<<endl; // actually performing a complicated algorithm here
    }
};

class demo : public test
{
public: 
    //test obj1;     // No need for this since you inherit from test
    // obj1.func();  // Not ok. You can't call a function in a class definition
};

void main()
{
    // There are no static functions. You need to create an object
    //demo::obj1.func();// getting an error here

    demo myObject;
    myObject.func();
}

Answer 2

实际上“使用继承从不同的类调用对象成员”，基本函数已经具有该函数（它继承了该函数）

class demo :public test
{
};

int main(int argc, char** argv)
{
  demo obj;
  obj.func();
}

你也可以这样做：

将;放在每个班级的末尾。
obj1.func()必须使用其他功能或其他内容......

尝试：

class demo :public test
{
public: 
test obj1;
demo() {obj1.func();}
};

或

class demo :public test
{
public: 
test obj1;
void callObj1Func() {obj1.func();}
};

并分别将其称为demo obj; demo obj; obj.callObj1Func();

使用::

进行调用时将其设为静态

Answer 3

你应该有demo个实例。然后打电话给其成员。

#include <iostream>
#include <string>

using namespace std;

class test
{
public: 
    void func()
    { 
        cout<<"test print"<<endl; // actually performing a complicated algorithm here
    }
};

class demo :public test
{
public: 
    test obj1;
};

int main()
{
    demo obj2;
    obj2.obj1.func();
    return 1;
}

如何从不同的类调用对象成员？

3 个答案: