超出最大调用堆栈大小 - 没有明显的递归
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【中文标题】超出最大调用堆栈大小 - 没有明显的递归【英文标题】:maximum call stack size exceeded - no apparent recursion 【发布时间】:2013-12-26 02:54:07 【问题描述】:我花了大约 12 个小时来查看这段代码并摆弄它,试图找出递归问题的所在,因为我得到了“超出最大调用堆栈大小”的错误,但没有找到了。请比我聪明的人帮助我!
到目前为止,我发现当我创建对象spot
、circle
对象时,问题消失了,但是当我将其设置为“pip”时,我得到了这个堆栈溢出错误。我已经用该死的显微镜检查了 pip 课程,但仍然不知道为什么会发生这种情况!
var canvas = document.getElementById('myCanvas');
//-------------------------------------------------------------------------------------
// Classes
//-------------------------------------------------------------------------------------
//=====================================================================================
//CLASS - point
function point(x,y)
this.x = x;
this.y = y;
//=====================================================================================
// CLASS - drawableItem
function drawableItem()
var size = 0;
this.center = new point(0,0);
this.lineWidth = 1;
this.dependentDrawableItems = new Array();
//returns the size
drawableItem.prototype.getSize = function getSize()
return this.size;
// changes the size of this item and the relative size of all dependents
drawableItem.prototype.changeSize = function(newSize)
var relativeItemSizes = new Array;
relativeItemSizes.length = this.dependentDrawableItems.length;
// get the relative size of all dependent items
for (var i = 0; i < this.dependentDrawableItems.length; i++)
relativeItemSizes[i] = this.dependentDrawableItems[i].getSize() / this.size;
// change the size
this.size = newSize;
// apply the ratio of change back to all dependent items
for (var i = 0; i < relativeItemSizes.length; i++)
this.dependentDrawableItems[i].changeSize(relativeItemSizes[i] * newSize);
//moves all the vertices and every dependent to an absolute point based on center
drawableItem.prototype.moveTo = function(moveX,moveY)
//record relative coordinates
var relativeItems = new Array;
relativeItems.length = this.dependentDrawableItems.length;
for (var i = 0; i < relativeItems.length; i++)
relativeItems[i] = new point;
relativeItems[i].x = this.dependentDrawableItems[i].center.x - this.center.x;
relativeItems[i].y = this.dependentDrawableItems[i].center.y - this.center.y;
//move the center
this.center.x = moveX;
this.center.y = moveY;
//move all the items relative to the center
for (var i = 0; i < relativeItems.length; i++)
this.dependentDrawableItems[i].moveItemTo(this.center.x + relativeItems[i].x,
this.center.y + relativeItems[i].y);
// draws every object in dependentDrawableItems
drawableItem.prototype.draw = function(ctx)
for (var i = 0; i < this.dependentDrawableItems.length; i++)
this.dependentDrawableItems[i].draw(ctx);
//=====================================================================================
//CLASS - circle
function circle(isFilledCircle)
drawableItem.call(this);
this.isFilled = isFilledCircle
circle.prototype = new drawableItem();
circle.prototype.parent = drawableItem.prototype;
circle.prototype.constructor = circle;
circle.prototype.draw = function(ctx)
ctx.moveTo(this.center.x,this.center.y);
ctx.beginPath();
ctx.arc(this.center.x, this.center.y, this.size, 0, 2*Math.PI);
ctx.closePath();
ctx.lineWidth = this.lineWidth;
ctx.strokeStyle = this.outlineColor;
if (this.isFilled === true)
ctx.fill();
else
ctx.stroke();
this.parent.draw.call(this,ctx);
//=====================================================================================
//CLASS - pip
function pip(size)
circle.call(this,true);
pip.prototype = new circle(false);
pip.prototype.parent = circle.prototype;
pip.prototype.constructor = pip;
//----------------------------------------------------------------------
// Objects/variables - top layer is last (except drawable area is first)
//----------------------------------------------------------------------
var drawableArea = new drawableItem();
var spot = new pip();
spot.changeSize(20);
drawableArea.dependentDrawableItems[drawableArea.dependentDrawableItems.length] = spot;
//------------------------------------------
// Draw loop
//------------------------------------------
function drawScreen()
var context = canvas.getContext('2d');
context.canvas.width = window.innerWidth;
context.canvas.height = window.innerHeight;
spot.moveTo(context.canvas.width/2, context.canvas.height/2);
drawableArea.draw(context);
window.addEventListener('resize', drawScreen);
这是演示:http://jsfiddle.net/DSU8w/
【问题讨论】:
还不够好,无法回答,但我偷偷怀疑你有一些非构造函数试图充当构造函数。 Google 闭包引发了一些关于Property getSize never defined
的问题,并且一些函数不是构造函数!看看***.com/a/5991265/588079 和***.com/a/4613017/588079 和***.com/q/6095530/588079。看看这是否有帮助,否则请尝试剪切部分代码,直到你有最低限度的溢出并在小提琴中分享它。
WARNING(对于其他专家):这个 sn-p 可能会使您的浏览器崩溃(我的浏览器崩溃了两次),所以不要摆弄如果您有重要的东西打开/未备份(例如其他 jsfiddle)。 @jgrant:尽量不要让小提琴自动运行,而是在点击按钮等清晰的用户操作后自动运行,从而让人们有机会实际加载小提琴并在加载崩溃之前检查源代码。
我猜是“drawableItem.prototype.changeSize”导致了你的问题。
@GitaarLAB - getSize 错误来自我删除的缺失方法,以及数百行其他代码,试图将代码缩减到最低限度 Aadit - 感谢您添加小提琴。
【参考方案1】:
this.parent.draw.call(this,ctx);
是你的问题。在pip
对象上,父对象将是circle.prototype
。所以当你现在调用spot.draw()
时,它会调用spot.parent.draw.call(spot)
,其中this.parent
仍然是circle.prototype
...
您需要从circle.prototype.draw
显式调用drawableItem.prototype.draw.call(this)
。顺便说一句,你应该not use new
for the prototype chain。
【讨论】:
我开始研究为什么不使用“新”和替代品......现在我的大脑正在融化。【参考方案2】:你为什么要写这样的代码?很难理解和调试。当我创建很多类时,我通常使用augment
来构建我的代码。这就是我将重写您的代码的方式:
var Point = Object.augment(function ()
this.constructor = function (x, y)
this.x = x;
this.y = y;
;
);
使用augment
,您可以干净地创建类。例如,您的 drawableItem
类可以重组如下:
var DrawableItem = Object.augment(function ()
this.constructor = function ()
this.size = 0;
this.lineWidth = 1;
this.dependencies = [];
this.center = new Point(0, 0);
;
this.changeSize = function (toSize)
var fromSize = this.size;
var ratio = toSize / fromSize;
this.size = toSize;
var dependencies = this.dependencies;
var length = dependencies.length;
var index = 0;
while (index < length)
var dependency = dependencies[index++];
dependency.changeSize(dependency.size * ratio);
;
this.moveTo = function (x, y)
var center = this.center;
var dx = x - center.x;
var dy = y - center.y;
center.x = x;
center.y = y;
var dependencies = this.dependencies;
var length = dependencies.length;
var index = 0;
while (index < length)
var dependency = dependencies[index++];
var center = dependency.center;
dependency.moveTo(center.x + dx, center.y + dy);
;
this.draw = function (context)
var dependencies = this.dependencies;
var length = dependencies.length;
var index = 0;
while (index < length) dependencies[index++].draw(context);
;
);
继承也很简单。例如,您可以重组 circle
和 pip
类,如下所示:
var Circle = DrawableItem.augment(function (base)
this.constructor = function (filled)
base.constructor.call(this);
this.filled = filled;
;
this.draw = function (context)
var center = this.center;
var x = center.x;
var y = center.y;
context.moveTo(x, y);
context.beginPath();
context.arc(x, y, this.size, 0, 2 * Math.PI);
context.closePath();
context.lineWidth = this.lineWidth;
context[this.filled ? "fill" : "stroke"]();
base.draw.call(this, context);
;
);
var Pip = Circle.augment(function (base)
this.constructor = function ()
base.constructor.call(this, true);
;
);
现在您已经创建了所有类,您终于可以开始画图了:
window.addEventListener("DOMContentLoaded", function ()
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var drawableArea = new DrawableItem;
var spot = new Pip;
spot.changeSize(20);
drawableArea.dependencies.push(spot);
window.addEventListener("resize", drawScreen, false);
drawScreen();
function drawScreen()
var width = canvas.width = window.innerWidth;
var height = canvas.height = window.innerHeight;
spot.moveTo(width / 2, height / 2);
drawableArea.draw(context);
, false);
我们完成了。亲自观看演示:http://jsfiddle.net/b5vNk/
我们不仅使您的代码更具可读性、可理解性和可维护性,而且还解决了您的递归问题。
正如 Bergi 所说,问题出在 circle.prototype.draw
函数中的声明 this.parent.draw.call(this,ctx)
上。因为spot.parent
是circle.prototype
,所以this.parent.draw.call(this,ctx)
语句等价于circle.prototype.draw.call(this,ctx)
。如您所见,circle.prototype.draw
函数现在递归调用自身,直到超过最大递归深度并引发错误。
augment
库优雅地解决了这个问题。当您扩充一个类 augment
时,不必在每个原型上创建一个 parent
属性,而是为您提供该类的 prototype
作为参数(我们称之为 base
):
var DerivedClass = BaseClass.augment(function (base)
console.log(base === BaseClass.prototype); // true
);
base
参数应被视为常量。因为它是上面Circle
类中的常量base.draw.call(this, context)
将始终等价于DrawableItem.prototype.draw.call(this, context)
。因此,您将永远不会有不需要的递归。与this.parent
不同,base
参数将始终指向正确的原型。
【讨论】:
【参考方案3】:Bergi 的回答是正确的,如果您不想多次硬编码父名称,可以使用辅助函数来设置继承:
function inherits(Child,Parent)
Child.prototype=Object.create(Parent.prototype);
Child.parent=Parent.prototype;
Child.prototype.constructor=Child;
;
function DrawableItem()
this.name="DrawableItem";
DrawableItem.prototype.changeSize = function(newSize)
console.log("changeSize from DrawableItem");
console.log("invoking object is:",this.name);
function Circle(isFilledCircle)
Circle.parent.constructor.call(this);
this.name="Circle";//override name
inherits(Circle,DrawableItem);
Circle.prototype.changeSize = function(newSize)
Circle.parent.changeSize.call(this);
console.log("and some more from circle");
;
function Pip(size)
Pip.parent.constructor.call(this,true);
this.name="Pip";
inherits(Pip,Circle);
var spot = new Pip();
spot.changeSize();
对于 Object.create 上的 polyfill,请查看 here。
【讨论】:
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