Question

我正在尝试为我的程序创建面向对象的方法。我读到这应该从Sprite创建一个World的继承，Sprite是父，但是Sprite.call（this，imagePath）出现，因为imagePath是未定义的。我会假设调用中的其他变量也是未定义的。如何正确调用父变量？

   function Sprite(spriteX, spriteY, spriteW, spriteH, scale, positionX, positionY, direction)
                {
                    this.imagePath = world_sprite;
                    this.spriteX = spriteX;
                    this.spriteY = spriteY;
                    this.spriteW = spriteW;
                    this.spriteH = spriteH;
                    this.scale = scale;
                    this.positionX = positionX;
                    this.positionY = positionY;
                    this.direction = direction;
                    this.speed = 5;

                    this.noGravity = false;
                    this.direction = 0;

                    //Physics stuff
                    this.velX = 0;
                    this.velY = 0;
                    this.friction = 0.98;
                };

    function World(posX, posY, direction, xOffset, yOffset)
                {
                    Sprite.call(this, imagePath, positionX, positionY, direction);

                    this.spriteX = 0;
                    this.spriteY = 0;
                    this.spriteW = 400;
                    this.spriteH = 400;
                    this.scale = 0.4;

                    this.xOffset = xOffset;
                    this.yOffset = yOffset;
                    this.lives = 3;
                };

Answer 1

这是你可以完成你想要做的事情的一种方式：

function Sprite(
   spriteX, spriteY, spriteW, spriteH,
   scale, positionX, positionY, direction
) {
    this.imagePath = world_sprite;
    this.spriteX = spriteX;
    this.spriteY = spriteY;
    this.spriteW = spriteW;
    this.spriteH = spriteH;
    this.scale = scale;
    this.positionX = positionX;
    this.positionY = positionY;
    this.direction = direction;
    this.speed = 5;

    this.noGravity = false;
    this.direction = 0;

    //Physics stuff
    this.velX = 0;
    this.velY = 0;
    this.friction = 0.98;
};

function World(
    posX, posY, direction, xOffset, yOffset
) {
    Sprite.call( this, 0, 0, 400, 400, 0.4, posX, posY, direction );

    this.xOffset = xOffset;
    this.yOffset = yOffset;
    this.lives = 3;
};

Answer 2

您有Sprite.call(this, imagePath, positionX, positionY, direction);，但Sprite的参数与此不匹配。

JavaScript继承Object.call（）未定义

2 个答案: