多态继承不覆盖基类方法 [英] Polymorphism inheritance not overriding base class method

问题描述

我的基类:

class Item
{
protected:  
    int count;
    string model_name;
    int item_number;

public:
    Item();
    void input();
}

我的派生类:

class Bed : public Item
{
private:
    string frame;
    string frameColour;
    string mattress;

public:
    Bed();
    void input();
}

现在我所有的输入函数都在尝试输出正在使用的方法:

for now all my input function is trying to do is output which method is being used:

void Item::input()
{ 
    cout<<"Item input"<<endl;
}

void Bed::input()
{
    cout<<" Bed Input"<<endl;
}

当我在 main 中调用函数时，我希望使用派生类输入，但目前项目输入是.

when I call the function in main I'd like the derived class input to be used but at present the item input is.

主要内容:

vector<Item> v;
Item* item;
item= new Bed;
v.push_back(*item);
v[count].input();
count++;

我遵循了我所拥有的书中介绍的方法，但我想我可能对如何创建存储在向量中的新对象感到困惑.

I have followed the method laid out in a book I have but I think i may be confused about how to create new objects stored in the vector.

任何帮助都会很棒，谢谢高

Any help would be great, Thanks Hx

推荐答案

您尚未将您的方法标记为 virtual.

You haven't marked your method as virtual.

此外，因为您有一个vector 对象，而不是指针，所以您会遇到对象切片.虽然它会编译，但它是不正确的.

Also, because you have a vector of objects, not pointers, you'll run into object slicing. Although it will compile, it isn't correct.

正确的方法是使用指针向量或智能指针.

The proper way is having a vector of pointers or smart pointers.

class Item
{
   //....
   virtual void input(); //mark method virtual in base class
};

class Bed : public Item
{
   //....
   virtual void input();
};


vector<Item*> v;
Item* item = new Bed;
v.push_back(item);
//...
//remember to free the memory
for ( int i = 0 ; i < v.size() ; i++ ) 
    delete v[i];

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