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访问当前对象的类(Access class of current object)

我正在实现一个virtual clone()方法,除了返回的对象的“实际”类型之外,它可以完全相同,我意识到会有很多重复。 例如,这是我想要避免的明显解决方案:

AbstractVehicle* ConcreteCar::clone() const
{
    auto c = new ConcreteCar;
    c->setSomething(this->getSomething());
    return c;
}

AbstractVehicle* ConcreteJet::clone() const
{
    auto j = new ConcreteJet;
    j->setSomething(this->getSomething());
    return j;
}

这就是我想要的:

AbstractVehicle* AbstractVehicle::clone() const
{
    auto v = new this->ACTUAL_CLASS;
    v->setSomething(this->getSomething());
    return v;
}

有没有直接的方法来做到这一点? 如果没有,我很想知道为什么会出现这种情况,因为天真地看起来实施起来并不比动态调度更具挑战性。


I'm implementing a virtual clone() method that can be entirely identical with the exception of the "actual" type of the object returned, and I realized that there's going to be a lot of duplication. For example, here's the obvious solution that I want to avoid:

AbstractVehicle* ConcreteCar::clone() const
{
    auto c = new ConcreteCar;
    c->setSomething(this->getSomething());
    return c;
}

AbstractVehicle* ConcreteJet::clone() const
{
    auto j = new ConcreteJet;
    j->setSomething(this->getSomething());
    return j;
}

And here's what I would like:

AbstractVehicle* AbstractVehicle::clone() const
{
    auto v = new this->ACTUAL_CLASS;
    v->setSomething(this->getSomething());
    return v;
}

Is there any straightforward way to do this? If not, I'd love to know why this is the case, because naively it does not seem like more of a challenge to implement than something like dynamic dispatch.


原文:https://stackoverflow.com/questions/33714506
更新时间:2020-02-28 15:55

最满意答案

根据您定义的setSomething / getSomething函数的小时数,您可以保留单个克隆,并且只需覆盖“创建我”类型函数。 例如:

AbstractVehicle* ConcreteCar::MakeNew() {    // virtual method
   return new ConcreteCar();
}

这将从基类克隆调用:

AbstractVehicle* AbstractVehicle::Clone() {
    auto j = MakeNew();
    j->setSomething(this->getSomething());
    return j;
}

Depending on hour your setSomething/getSomething functions are defined, you may be able keep a single clone, and just have overrides on a 'create me' type function. For example:

AbstractVehicle* ConcreteCar::MakeNew() {    // virtual method
   return new ConcreteCar();
}

This would be called from the base class clone:

AbstractVehicle* AbstractVehicle::Clone() {
    auto j = MakeNew();
    j->setSomething(this->getSomething());
    return j;
}
2015-11-15

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