How to call the function in derived class to process handle_post?(Function call missing argument list to create pointer)

Question

在我的基础class中，这是一个public非静态成员函数：

void BaseClass::SetPorcessMethod()
{
     //do something
    Listener.support(methods::POST, this->HandlePost);
    //do something
}

在上面的函数中，Listener是一个静态成员变量。函数 HandlePost 是一个纯虚函数，由所有派生的 classes 实现。我想使用 this 指针从不同的派生 class 调用不同的 HandlePost。喜欢：

class BaseClass
{
 public:
   static http_listener listener;
   void SetPorcessMethod();
   virtual void HandlePost((http_request request) = 0;
   /*listener is init in constructor , not display here*/
}
 class Derived2:public BaseClass
{
  void HandlePost(http_request request);
}
class Derived1:public BaseClass
{
  void HandlePost(http_request request);
}

Derived1 instance1;
instance1.SetPorcessMethod();
Derived2 instance2;
instance2.SetPorcessMethod();

但是显示BaseClass::HandlePost:function call missing argument list use &BaseClass::HandlePost:function to create a pointer to member。我知道这是因为Your code attempts to pass a pointer-to-member-function, which cannot be converted to a pointer-to-function. This is because a pointer-to-member-function can only be called on an object, so it wouldn't know what object to use. Function call missing argument list to create pointer 但是我应该怎么做才能用 support() 从派生的 class 调用函数？

Answer 1

您正在尝试将成员函数传递给 support。为了调用这样的函数，调用者需要成员函数参数和指向调用函数的实例的指针。

然而 support 需要一个 std::function<void(http_request)>，即没有实例指针。因此，您必须将调用包装到另一个不需要传递 BaseClass 实例指针的可调用对象中。您可以使用 lambda（如果您愿意，也可以使用 std::bind）：

Listener.support( methods::POST,
    [this](http_request request){return HandlePost(request);} );

Listener.support( methods::POST,
    std::bind(&BaseClass::HandlePost, this, std::placeholders::_1) );

#include<functional> 用于后一种变体。

How to call the function in derived class to process handle_post?(Function call missing argument list to create pointer)

How to call the function in derived class to process handle_post?(Function call missing argument list to create pointer)

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