从子类中的基类添加构造函数

Posted 2023-02-23

【中文标题】从子类中的基类添加构造函数

【英文标题】：Add upon constructor from base class in subclass

【发布时间】：2020-12-24 20:34:24

【问题描述】：

当我遇到问题时，我正在处理 c++ 类。我试图让一个玩家类继承自 Entity 类并混合它们的构造函数。实体类有一个构造函数，要求您提供 x 位置浮动和 y 位置浮动。我希望 Player 类也需要 x 和 y 位置，但我也希望名称是必需的。我该怎么做？

这是我的代码：

#include <iostream>

class Entity
public:
    float x, y;
    int health = 30;
    
    Entity(float X, float Y)
        std::cout << "Entity Constructed!" << std::endl;
        x = X;
        y = Y;
    
    
    ~Entity()
        std::cout << "Entity Destructed!" << std::endl;
    
    
    void Print()
        std::cout << x << ", " << y << std::endl;
    
    
    void Move(float mx, float my)
        x+=mx;
        y+=my;
    
;

class Player : public Entity
public:
    const char* Name;
    int attack_damage = 5;
    
    Player(const char* name)
        Name = name;
    
    
    void Attack(Entity& entity)
        entity.health-=attack_damage;
    
;

int main()
    Entity e(0.0f, 0.0f);
    Player p(0.0f,0.0f);
    std::cout << e.health << std::endl;
    p.Attack(e);
    std::cout << e.health << std::endl;
    std::cin.get();

这是我在尝试编译上面提供的代码时收到的错误消息：

FAILED: CMakeFiles/learning-cpp.dir/src/main.cpp.o 
/usr/bin/c++    -Wall -Werror -std=c++14 -g -MD -MT CMakeFiles/learning-cpp.dir/src/main.cpp.o -MF CMakeFiles/learning-cpp.dir/src/main.cpp.o.d -o CMakeFiles/learning-cpp.dir/src/main.cpp.o -c src/main.cpp
src/main.cpp: In constructor ‘Player::Player(const char*)’:
src/main.cpp:33:29: error: no matching function for call to ‘Entity::Entity()’
     Player(const char* name)
                             ^
src/main.cpp:8:5: note: candidate: ‘Entity::Entity(float, float)’
     Entity(float X, float Y)
     ^~~~~~
src/main.cpp:8:5: note:   candidate expects 2 arguments, 0 provided
src/main.cpp:3:7: note: candidate: ‘constexpr Entity::Entity(const Entity&)’
 class Entity
       ^~~~~~
src/main.cpp:3:7: note:   candidate expects 1 argument, 0 provided
src/main.cpp: In function ‘int main()’:
src/main.cpp:44:23: error: no matching function for call to ‘Player::Player(float, float)’
     Player p(0.0f,0.0f);
                       ^
src/main.cpp:33:5: note: candidate: ‘Player::Player(const char*)’
     Player(const char* name)
     ^~~~~~
src/main.cpp:33:5: note:   candidate expects 1 argument, 2 provided
src/main.cpp:28:7: note: candidate: ‘constexpr Player::Player(const Player&)’
 class Player : public Entity
       ^~~~~~
src/main.cpp:28:7: note:   candidate expects 1 argument, 2 provided
src/main.cpp:28:7: note: candidate: ‘constexpr Player::Player(Player&&)’
src/main.cpp:28:7: note:   candidate expects 1 argument, 2 provided
ninja: build stopped: subcommand failed.

【问题讨论】：

您需要在子类的初始化列表中提供基类的构造函数参数：Player(char const* name, double, x, double y): Entity(x, y), name(name) 。我发现我编写的大多数构造函数的主体都是空的，并且所有内容都从初始化列表中初始化。

啊，谢谢！我能够编辑它来工作。 :)

【参考方案1】：

试试这个

Player(float x, float y, const char* name)
    : Entity(x,y)

    Name = name;