C多态性/类依赖性错误[关闭]

1 回答

• 2

  您的 Child 类使用尚未定义的 Parent 类（不在代码上方，在 Child 之前或在某些包含的文件中） . 要解决此问题，请在（或"above"） Child 之前声明 Parent 类 . 例如：

  class Parent;
  
  //child class declaration as posted in your code and other classes include Parent.
  class Child{
  public:
      Child(Parent* parent, char* name) : par(parent), Name(name){ par->addChild(this); };
      Parent* par;
  ...
  

  希望这可以帮助 .

  [已添加]以下是作者提问的代码示例：

  #include <iostream>
  #include <vector>
  
  using namespace std;
  
  class Child;
  
  class Parent {
  
  public:
      Parent(const char* name) : Name(name){};
      const char* Name;
      std::vector<Child*> Children;
  
      void Speak(void);
      void addChild(Child* child);
  };
  
  class Child{
  public:
      Child(Parent* parent, const char* name) {
          Child::par = parent;
          Child::Name = name;
          par->addChild(this); 
      }
  
      Parent* par;
      const char* Name;
      virtual void Speak(void){
          std::cout << "I am a child, my name is " << Name << " and my parent's name is " << par->Name << std::endl;
      }
  };
  
  void Parent::Speak(void){
          std::cout << "I am a parent called " << Name << std::endl;
          if(Children.size() == 0){
              std::cout << "I have no children" << std::endl;
          }
          else{
              std::cout << "I have " << Children.size() << " child(ren):" << std::endl;
              for(auto c : Children){
                  std::cout << c->Name << std::endl;
              }
          }
      }
  
  
  void Parent::addChild(Child* child) {
          Children.push_back(child);
      }
  
  class Father : public Parent{
  public:
      Father(const char* name) : Parent(name){}
      void Speak(void){
          std::cout << "I am a father called " << Name << std::endl;
          if(Children.size() == 0){
              std::cout << "I have no children" << std::endl;
          }
          else{
              std::cout << "I have " << Children.size() << "child(ren):" << std::endl;
              for(auto c : Children){
                  std::cout << c->Name << std::endl;
              }
          }
      }
  };
  
  class Son : public Child{
  public:
      Son(Parent* parent, const char* name) : Child(parent, name){}
      void Speak(void){
          std::cout << "I am a son, my name is " << Name << " and my parent's name is " << par->Name << std::endl;
      }
  };
  
  int main(int argc, char** argv){
  
      //i suggest you to use stack-located variables against heap-located
      Father Dad("James");
      Dad.Speak();
  
      Son John(&Dad, "John");
      John.Speak();
      Dad.Speak();    
  
      // Father* Dad = new Father("James");
      // Dad->Speak();
      // Son* John = new Son(Dad, "John");
      // John->Speak();
      // Dad->Speak();
      // delete Dad; 
      // delete John;
      //getchar();
      return (0);
  }
  

  输出online cpp editor

  Compiling the source code....
  $g++ -std=c++11 main.cpp -o demo -lm -pthread -lgmpxx -lgmp -lreadline 2>&1
  
  Executing the program....
  $demo 
  I am a father called James
  I have no children
  I am a son, my name is John and my parent's name is James
  I am a father called James
  I have 1child(ren):
  John
  

  回复于 2024-04-27T11:22:46+08:00