在C ++ / QT中创建抽象类对象的QList？ [英] Making a QList of an abstract class objects in C++/QT?

问题描述

尽管这里的其他问题/答案已经无数次地帮助了我，但这是我的第一个问题，所以请不要对我太苛刻！ ：）

although I've been helped countless times by other questions/answers here, this is my first question here, so don't be too harsh on me! :)

我一直在学习QT / C ++，并假设我有这样的东西：

I've been learning QT/C++ and let's assume I have something like this:

class AbstractMasterClass{
public:
    virtual void foo(void) = 0;   //Pure virtual method
}

该类将有很多子类，每个子类实现自己的foo（）方法。
问题是：如何创建一个将用AbstractMasterClass的子类填充的QList？

This class will have plenty subclasses, each one of them implementing their own foo() method. And the question is: How can I create a QList which I'll populate with AbstractMasterClass's subclasses?

目标是能够遍历列表为每个元素调用foo（）方法，即使用主类，就像我对Java接口所做的一样。
经过几次尝试，我最终遇到了几个编译时错误，这些错误表明我们在创建QList时无法（显然）分配抽象类的对象。

The objective is to be able to iterate through the list calling the foo() method for every element, i.e. use the master class the same way I would do to a Java interface. The few tries I ended up getting several compile time errors saying that we can't allocate an object of an abstract class (obviously) while creating the QList.

那么我该怎么做，还是有更好的方法在C ++ / QT中制作类似Java的接口？

So how can I do it or is there a better way to make a java like interface in C++/QT?

在此先感谢大家的回答或指点。

Thank you all in advance for your time answering or pointing me in the right direction!

推荐答案

这是一个通用的C ++问题，而不是Qt问题。在这种情况下，您可能想使用多态性。创建类型为AbstractMasterClass的指针，并使其指向您的派生类之一，然后将指针存储在列表中。我在下面的示例中使用了QSharedPtr，以避免您需要手动删除内存。

This is a general C++ question more than a Qt issue. You would want to use polymorphism in this case. Create a pointer of type AbstractMasterClass and make it point to one of your derived classes, then you store the pointers in your list. I used QSharedPtr in the example below to avoid you needing to do any manual deletion of memory.

class AbstractMasterClass {
public:
    virtual ~AbstractMasterClass(){};  // virtual destructor so derived classes can clean up
    virtual void foo() = 0;
};

class DerivedA : public AbstractMasterClass {
public:
    void foo() { cout << "A\n"; }
};

class DerivedB : public AbstractMasterClass {
public:
    void foo() { cout << "B\n"; }
};

int main() {
    QList<QSharedPtr<AbstractMasterClass>> myList;

    QSharedPtr<AbstractMasterClass> a(new DerivedA());
    QSharedPtr<AbstractMasterClass> b(new DerivedB());

    myList.push_back(a);
    myList.push_back(b);

    for (auto &it : myList) {
        it->foo();
    }

    return 0;
}

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