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POJavascript inheritance idea (part 2)
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copied!<p>Okay, my first attempt at trying to explain what I was doing failed miserably. I'm basically copying Crockford's Object.create(), except with private variables.</p> <p>If you look at the accepted answer here <a href="https://stackoverflow.com/questions/2107556/how-to-inherit-from-a-class-in-javascript">How to inherit from a class in javascript?</a>, you will see Object.create as the last pattern, which I think better fits the prototypal nature of Javascript (objects beget objects) instead of emulating classical inheritance (classes beget objects).</p> <p>If you look at Wikipedia's article on prototype based programming (<a href="http://en.wikipedia.org/wiki/Prototype-based_programming" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Prototype-based_programming</a>), you can see more of what I mean.</p> <p>The drawback with Object.create() though is that there is no support for private members. This is what I propose:</p> <pre><code>Function.prototype.from = function(obj) { function F() {this.parent = Object(obj);} F.prototype = obj; var out = new F(); this.apply(out); return out; }; </code></pre> <p>Then, you create objects as thus:</p> <pre><code>// Create an object var a = function() { var private_property = 'blue'; this.public_property = 7; this.public_method = function() { alert(this.public_property + ' ' + private_property); } }.from(null); // .from() works too, but .from(null) is more revealing // Create a new object using 'a' as the prototype var b = function() { var private_property = 'red'; this.public_property = 8; }.from(a); // See the results a.public_method(); // Alerts '7 blue' b.public_method(); // Alerts '8 blue' - Parent methods use parent private variables a.public_method = function() { alert('rabbit'); }; a.public_method(); // Alerts 'rabbit' b.public_method(); // Alerts 'rabbit' b.public_method = function() { alert('dog'); }; a.public_method(); // Alerts 'rabbit' b.public_method(); // Alerts 'dog' - Parent method is overwritten </code></pre> <p>The way I made the "from" function is such that when a parent object changes its methods, if you want to prevent the change in a child instance, you can specify:</p> <pre><code>this.public_method = this.parent.public_method; </code></pre> <p>in the child instance.</p> <p><strike>Note also that objects created ex nihilo do not inherit from Object (hasOwnProperty, etc..). You must explicitly specify this as .from(Object).</strike></p> <p>Benefits of this pattern:</p> <ol> <li>Memory is not wasted for each new instance</li> <li>It adheres to a <em>true</em> prototypal inheritance pattern</li> <li>You have access to the parent object using this.parent (this.__proto__ is browser specific)</li> <li>Private variables now exist</li> </ol> <p>There is one major drawback of this method that I can think of: the 'function()' syntax may confuse people into thinking a function is assigned to the variable instead of an object.</p> <p>My question is, are there other drawbacks that I am missing? (Don't include drawbacks of the prototypal pattern--that's subjective--but only of my implementation).</p>

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