C++未声明的标识符错误

Question

我得到一个未声明的标识符错误，我不知道为什么。我甚至重写了完整的内容，以确保我没有输入错字。有人能告诉我为什么我有这个错误吗？

我的文件

Connection.hpp

#pragma once 

#include "../LogicSimulator.hpp" 
#include "CircuitObject.hpp" 

class Connection 
{ 
public: 
    Connection(CircuitObject& c1, CircuitObject& c2, LogicSimulator& 
     simulator); 
private: 
    int state; 
    CircuitObject& c1; 
    CircuitObject& c2; 
    LogicSimulator& simulator; 
}; 

不介意CircuitObjects，他们不给任何错误，错误：未声明 'LogicSimulator'

Connection.cpp

#pragma once 

#include "Connection.hpp" 
#include "../LogicSimulator.hpp" 
#include "CircuitObject.hpp" 

Connection::Connection(CircuitObject& c1, CircuitObject& c2, LogicSimulator& 
    simulator) : c1(c1), c2(c2), simulator(simulator) 
{ 
    state = c1.State; 
} 

个

错误：未申报 'LogicSimulator'

LogicSimulator.hpp

#pragma once 

#include "Simulator\CircuitObject.hpp" 
#include "Simulator\Connection.hpp" 
#include <SFML\Graphics.hpp> 
#include <vector> 

class LogicSimulator 
{ 
public: 
    std::vector<CircuitObject*> circuitObjects; 
    std::vector<CircuitObject*> selectedCircuitObjects; 
    std::vector<Connection*> connections; 
    sf::RenderWindow Window; 

    void Init(); 
private: 
    void start(); 
    void draw(); 
}; 

不介意LogicSimulator.cpp，它不发出任何错误。

---

错误：未申报的“连接”（是的，在连接LogicSimulator是不宣）

Answer 1

这是，正如我在评论中写道，极有可能造成你的循环包括。 Connection.hpp包括LogicSimulator.hpp，其本身包括Connection.hpp。

就你而言，你甚至不需要包含。对于指针和引用，预先声明是好的：

Connection.hpp：

#pragma once 

class CircuitObject; 
class LogicSimulator; 

class Connection 
{ 
public: 
    Connection(CircuitObject& c1, CircuitObject& c2, LogicSimulator& 
     simulator); 
private: 
    int state; 
    CircuitObject& c1; 
    CircuitObject& c2; 
    LogicSimulator& simulator; 
}; 

LogicSimulator.hpp：

#pragma once 

#include <SFML\Graphics.hpp> 
#include <vector> 

class CircuitObject; 
class Connection; 

class LogicSimulator 
{ 
public: 
    std::vector<CircuitObject*> circuitObjects; 
    std::vector<CircuitObject*> selectedCircuitObjects; 
    std::vector<Connection*> connections; 
    sf::RenderWindow Window; 

    void Init(); 
private: 
    void start(); 
    void draw(); 
};