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POJavascript Prototype Problems
 

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    <p>My situation is that I am working on a Canvas game using Box2DWeb, so I have a class called <em>Sprite</em> that draws an image to the Canvas, I now want to create a <em>PhysicsSprite</em> class that inherits methods and properties from <em>Sprite</em>.</p> <p>My <em>Sprite</em> class (Sprite.js):</p> <pre><code>Sprite = function (position, dimension, image) { this.Position = position; this.Dimension = dimension; if (image) this.Image = image; ... this.Draw = function (g) { ... } ... }; </code></pre> <p>And I am setting the prototype in <em>PhysicsSprite</em> (PhysicsSprite.js) like so:</p> <pre><code>PhysicsSprite = function(position, dimension, world) { this.prototype = new Sprite(position, dimension, undefined); //alert(this.prototype.Position.X) var body = CreateBody(); this.GetBody = function () { return body; } this.Draw = function (g) { ... } function CreateBody () { ... } }; </code></pre> <p>Note the <strong>alert(this.prototype.Position.X)</strong>, which does alert me of the position, but if I change the code to <strong>this.Position.X</strong>, I get an error, and similarly, if I have an instance of <em>PhysicsSprite</em>, I have to explicitly call the prototype.</p> <p>This lead me to think that I haven't set the Object's prototype, merely created a property called <code>prototype</code>, and set that to a new <em>Sprite</em>.</p> <p>If someone could help me, and explain what I am doing wrong, that would be much appreciated. I am dyslexic, so I always misspell variables, which is frustrating, so that was the first thing I looked for, but everything looks fine to me.</p>
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    1. USCheran Shunmugavel
    1. USLuke O'Brien
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    1. COYou are right. I recommend to have a look at the MDN documentation for examples: https://developer.mozilla.org/en/JavaScript/Guide/Inheritance_constructor_prototype and https://developer.mozilla.org/en/JavaScript/Guide/Inheritance_Revisited. This question might help as well: http://stackoverflow.com/questions/7944880/js-confusion-about-inheritance
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      1. USFelix Kling
 

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