C++继承方法但返回类型错误(自动转换？typeid(*this)？)

Question

我有一个BaseClass,其方法返回一个类对象,我有一个DerivedClass.现在,当我有一个DerivedClass对象并调用BaseClass中定义的方法时,返回值是ob类型BaseClass,遗憾的是不是DerivedClass类型.

class BaseClass {
public:
  typeof(*this) myMethod1() {return *this;} // nice if that would work
  BaseClass& myMethod2() {return *this;}
  BaseClass myMethod3() {return BaseClass();}
};
class DerivedClass : public BaseClass {};

DerivedClass tmp;
tmp.myMethod1();
tmp.myMethod2();
tmp.myMethod3();
// all three methods should return an object of type DerivedClass,
// but really they return an object of type BaseClass

所以我希望实现的是使用超类的方法,但是使用派生类的返回类型(自动转换？).myMethod1()是我唯一能想到的,但它不起作用.

我搜索过但没有找到任何令人满意的东西.

Answer 1

您想使用CRTP(http://en.wikipedia.org/wiki/Curiously_recurring_template_pattern)模式:

template <class Derived>
class BaseClass {
public:
  Derived *myMethod1() {return static_cast<Derived *>(this);}
  Derived& myMethod2() {return static_cast<Derived&>(*this);}
};
class DerivedClass : public BaseClass<DerivedClass> {};

DerivedClass tmp;
tmp.myMethod1();
tmp.myMethod2();