C++ SFML对象不会绘制

-1

在下面的代码中，我尝试在复合对象中绘制圆形对象，但它不会绘制。我不知道为什么。此代码永远不会达到圆形绘制方法。C++ SFML对象不会绘制

如果我称之为main.cpp中圆的draw（）方法直接将画..

drawable.h

#pragma once 

#include <SFML/Graphics.hpp> 

class drawable{ 
    public: 
    drawable(sf::Vector2f position); 
    virtual void draw(sf::RenderWindow & window){}; 
    sf::Vector2f position; 
}; 

class circle : public drawable{ 
    public: 
    circle(sf::Vector2f position); 
    void draw(sf::RenderWindow & window) override; 
}; 

class composite : public drawable{ 
    public: 
    composite(sf::Vector2f position, drawable part); 
    void draw(sf::RenderWindow & window) override; 
    private: 
    int count = 0; 
    drawable part; 
};

drawable.cpp

#include "drawable.h" 

#include <iostream> 
using namespace std; 

drawable::drawable(sf::Vector2f position) : position{ position } { 
} 

circle::circle(sf::Vector2f position) : drawable{ position } { 
} 

composite::composite(sf::Vector2f position, drawable part) : drawable(position), part{ part }{ 
} 

void circle::draw(sf::RenderWindow & window) { 
    sf::CircleShape circle; 
    circle.setPosition(position); 
    circle.setRadius(30); 
    window.draw(circle); 
} 

void composite::draw(sf::RenderWindow & window) { 
    this->part.position.x = this->position.x + part.position.x; 
    this->part.position.y = this->position.y + part.position.y; 
    this->part.draw(window); 
}

为主。 cpp

#include <SFML/Graphics.hpp> 
#include "drawable.h" 

int main() 
{ 
    sf::RenderWindow window = sf::RenderWindow{ sf::VideoMode{ 640, 480 }, "SFML window" }; 

    circle circle{ sf::Vector2f{ 100, 200 } }; 
    composite composite(sf::Vector2f{ 200, 200 }, circle); 

    window.clear(); 
    composite.draw(window); 
    window.display(); 

    while (window.isOpen()) { 
    sf::Event event; 
    while (window.pollEvent(event)){ 
     if (event.type == sf::Event::Closed){ 
      window.close(); 
     } 
    } 
    sf::sleep(sf::milliseconds(20)); 
    } 

    return 0; 
}

来源

2014-10-07 ZxCvBnM

Composite按价值取drawable。这意味着在composite里面，你只能得到drawable的对象;所有关于具体类型的信息都会丢失。如果你想支持多态对象，你需要使用指针或引用。

来源

2014-10-07 21:02:55

C++ SFML对象不会绘制

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