c ++，未在此范围内声明

Question

我正在尝试创建游戏，但我的功能存在一些问题。

在包含以下内容的行上：myBeem.setBeemLocation（50，50）; 我收到以下错误：在此范围内未声明myBeem

为什么？

干杯

---

#include <SFML/Graphics.hpp>
#include <SFML/Window.hpp>
#include <iostream>
#include <SFML/Audio.hpp>

using namespace std;

//WINDOW
sf::VideoMode VMode(800, 600, 32);
sf::RenderWindow Window(VMode, "Space Defender");


class laserbeem{

public:
    laserbeem();
    ~laserbeem();
    void setBeemLocation(float x, float y);

protected:
    float beemLocationX;
    float beemLocationY;

};

laserbeem::laserbeem(){
}

laserbeem::~laserbeem(){
}

void laserbeem::setBeemLocation(float x, float y){

    beemLocationX = x;
    beemLocationY = y;
}


int main()
{


    //MUSIC
    sf::Music music;
    if (!music.openFromFile("music.ogg"))
        std::cout << "Music failed to load!" << std::endl;
    music.play();

    //SOUNDS
    sf::SoundBuffer buffer;
    if (!buffer.loadFromFile("laser.ogg"))
        std::cout << "Laser failed to load!" << std::endl;
    //return 0;

    sf::Sound laser;
    laser.setBuffer(buffer);


    //BACKGROUND
    sf::Texture Image;
    if (!Image.loadFromFile("gal.jpg"))
    {
        std::cout << "Image failed to load!" << std::endl;
        return 1;
    }

    sf::Sprite Sprite;
    Sprite.setTexture(Image);

    Sprite.setPosition(0.0f, 0.0f);
    Sprite.setScale((float)VMode.width/(float)Sprite.getTexture()->getSize().x, (float)VMode.height/(float)Sprite.getTexture()->getSize().y);

    //Sprite.setScale((float)VMode.width, (float)VMode.height);
    //Sprite.setPosition(100.0f, 30.0f);
    //Sprite.setScale(.5f, .3f);

    //SHIP
    sf::Texture Image2;
    if (!Image2.loadFromFile("ship.png"))
        return 1;

    sf::Sprite Sprite2;
    Sprite2.setTexture(Image2);

    //float x = 400.0;
    Sprite2.setPosition(400.0f, 450.0f);
    Sprite2.setScale(.8f, .8f);


while (Window.isOpen())
{
    sf::Event Event;
    while (Window.pollEvent(Event))
    {
    switch (Event.type)
    {
    case sf::Event::Closed:
        Window.close();
        std::cout << "The window was closed." << std::endl;
        break;

    case sf::Event::KeyPressed:
        //LEFT KEY
        if (Event.key.code == sf::Keyboard::Left)
        Sprite2.move(-15,0);
        //RIGHT KEY
        if (Event.key.code == sf::Keyboard::Right)
        Sprite2.move(15,0);
        //UP KEY
        if (Event.key.code == sf::Keyboard::Up)
        Sprite2.move(0,-15);
        //DOWN KEY
        if (Event.key.code == sf::Keyboard::Down)
        Sprite2.move(0,15);
        //LEFT CTRL KEY
        if (Event.key.code == sf::Keyboard::LControl)
        laserbeem myBeem;
        myBeem.setBeemLocation(50, 50);
        laser.play();
    break;

    default:
        break;
    }
}

Window.clear(sf::Color(144, 144, 144));
Window.draw(Sprite);
Window.draw(Sprite2);
Window.display();
}

    return 0;
}

Answer 1

下列：

    if (Event.key.code == sf::Keyboard::LControl)
    laserbeem myBeem;
    myBeem.setBeemLocation(50, 50);

等效于：

    if (Event.key.code == sf::Keyboard::LControl) {
      laserbeem myBeem;
    }
    // myBeem no longer exists
    myBeem.setBeemLocation(50, 50);

换句话说， myBeem的范围仅限于if语句中的块。

您需要重新检查花括号在代码中的位置（以及使用缩进，以提高可读性）。

Answer 2

在您的big switch语句中，应该给包含有错误行的case语句提供自己的块，如下所示：

case sf::Event::KeyPressed:
{
    //LEFT KEY
    if (Event.key.code == sf::Keyboard::Left)
        Sprite2.move(-15,0);
    //RIGHT KEY
    if (Event.key.code == sf::Keyboard::Right)
        Sprite2.move(15,0);
    //UP KEY
    if (Event.key.code == sf::Keyboard::Up)
        Sprite2.move(0,-15);
    //DOWN KEY
    if (Event.key.code == sf::Keyboard::Down)
        Sprite2.move(0,15);
    //LEFT CTRL KEY
    if (Event.key.code == sf::Keyboard::LControl)
    laserbeem myBeem;
    myBeem.setBeemLocation(50, 50);
    laser.play();
    break;
}

而且，只是说，“ beem”应拼写为“ beam”。