如何解决未捕获的错误:无法读取未定义的属性 x
我正在使用 matter.js 和 p5.js 制作这个游戏,你必须使用弹弓和石头让芒果从树上掉下来。代码看起来有点像这样:
SlingShot.js:
constructor(bodyAInput,pointBInput) {
var options = {
bodyA: bodyAInput,pointB: pointBInput,stiffness: 0.2,length: 20
}
this.pointB = pointBInput;
this.constraint = Matter.Constraint.create(options);
World.add(world,this.constraint);
}
detach() {
this.constraint.bodyA = null;
}
attach(bodyInput) {
this.constraint.bodyA = bodyInput;
}
display() {
var pointA = this.constraint.bodyA.position;
var pointB = this.pointB;
line(pointA.x -40,pointA.y,pointB.x - 40,pointB.y);
line(pointA.x,pointB.x,pointB.y - 3);
}
}
Sketch.js(出现错误的相关部分):
function setup() {
createCanvas(1300,600);
engine = Engine.create();
world = engine.world;
mango1 = new mango(1100,100,30);
mango2 = new mango(1000,150,30);
mango3 = new mango(900,200,30);
mango4 = new mango(950,250,30);
mango5 = new mango(1200,30);
stoneObj = new Stone(230,400);
treeObj = new tree(1050,580);
groundobject = new ground(width / 2,600,width,20);
//console.log(SlingShot);
launcherObject = new SlingShot( stoneObj,{ x:230,y: 400 });
Engine.run(engine);
}
matter.js:7769 Uncaught TypeError: Cannot read property 'x' of undefined
at Object.Vector.add (matter.js:7769)
at Object.Constraint.create (matter.js:3597)
at new SlingShot (slingShot.js:12)
at setup (sketch.js:32)
at _setup (p5.js:58811)
at _runIfPreloadsAreDone (p5.js:58752)
at p5._decrementPreload (p5.js:58761)
at Image.img.onload (p5.js:74562)
编辑:这是 Stone.js 的代码:
class Stone{
constructor(x,y){
var options = {
isstatic: true
}
this.body = Bodies.circle(x,y,10,options);
World.add(world,this.body);
this.image = loadImage("images/stone.png");
}
display(){
push ();
image(this.image,this.body.position.x,this.body.position.y,20,20);
pop ();
}
}
解决方法
创建 SlingShot
时,stoneObj
是构造函数的第一个参数
let launcherObject = new SlingShot( stoneObj,{ x:230,y: 400 });
第一个参数是 bodyAInput
,它被分配给 options.bodyA
,它需要是一个 Body
对象。
constructor(bodyAInput,pointBInput) {
var options = {
bodyA: bodyAInput,pointB: pointBInput,stiffness: 0.2,length: 20
}
Stone
不是 Body
对象,但它有一个 Body
,因此需要像这样设置选项:
constructor(bodyAInput,pointBInput) {
var options = {
bodyA: bodyAInput.body,length: 20
}
,
问题在于您如何通过新的 SlingShot 类传递和读取 StoneObj。在 SlingShot 类中,您试图读取未定义的 pointA 的属性 x,可能是因为 StoneObj 没有返回您期望的位置。
尝试记录该部分以查看发生了什么问题。
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