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POObject.create Prototype Chains
 

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    <h1>Initial Question</h1> <p>Yesterday i read about ECMAScript 5 Object.create() And I wanted to start building prototype Chains in my Code with this method instead of setting the prototype and its constructor, I like that you can directly set writable configurable etc.. </p> <p>I tried it like this</p> <pre><code>function printobject(msg, obj) { if (msg) { document.write("&lt;b&gt;" + msg + "&lt;/b&gt;&lt;br&gt;"); document.write("&lt;hr&gt;&lt;br&gt;"); } for (var prop in obj) { if (obj.hasOwnProperty(prop)) { if (obj[prop].toString() !== "[object Object]") { document.write(prop + " : " + obj[prop] + "&lt;br&gt;"); } else { document.write("&lt;b&gt;" + prop + " : " + obj[prop] + "&lt;/b&gt;&lt;br&gt;"); printobject("", obj[prop]); } } } if (msg) { document.write("&lt;br&gt;&lt;hr&gt;&lt;br&gt;"); } }; var base = { extend: function () { //extend this Object var args = Array.prototype.slice.call(arguments); printobject("Arguments to Extend", args) var that = Object.create(this, (args ? args.shift() : {})); var arg = args.shift() || {}; printobject("Copy Properties to New Object", arg); for (var prop in arg) { that[prop] = arg[prop]; } // Object.freeze(that); return that; }, create: function () { //Creates new instances of the Object var that = Object.create(this, { extend: { value: null, writable: false, configurable: false }, //sets extend and create to null so you cant create a new instance when used create ( use extend instead); create: { value: null, writable: false, configurable: false } }); that.init.apply(that, arguments); //call init function for the new created object; return that; }, init: function () { printobject("No Initfunction supplied for New Object", this); } // Empty init function for fallback } var Human = base.extend({ name: { value: "test" } }, { init: function (name) { alert(name + " has been created"); this.name = name; }, walk: function () { alert(this.name + " walks"); } }); var Human1 = Human.create("test2"); //alert("Human1 - Name:" + Human1.name); Human1.walk(); Human.walk = function () { alert("Walk has been overwritten") }; //Object freezed Human1.walk(); Human1.create = function () { alert("Overwrite create"); }; //Doesnt exist in created Object Human1.create(); ? </code></pre> <ul> <li>Do the methods given in <code>Human</code> only exist once in the ram? and <code>Human1.walk()</code> points to it?</li> <li>I wonder if this is the right Approach of doing it like this? I'm relatively new to JavaScript.</li> </ul> <p>This is the code on <a href="http://jsfiddle.net/2VdJN/" rel="nofollow noreferrer"><strong>jsfiddle</strong></a>.</p> <h2>Answer</h2> <p>First of all, thx a lot that made things def clearer =) But, 1: when I do it like this the instances inherit from their constructor's prototype (?)</p> <pre><code> Nothing = {}; function base() { this.inherit = function(constructor) { alert("inherit"); var obj = constructor; obj.constructor = constructor; obj.prototype = this; return obj ; } ;} base.prototype = Nothing; base.constructor = base; var Top = new base(); var Human = Top.inherit(function(name) { this.name = name; }); var Paul = new Human("Paul"); alert(Paul.name); alert(Paul instanceof Human); //true ` </code></pre> <p>2: So the instanceof operator doesnt break in this Code , (that it works for functions only seems clear to me)</p> <p>But written this way, Paul still inherits the inherit() method from Top's prototype and i would need to overwrite it But if i dont want the instance of Human to inherit the method, how do i do this ?</p> <p>And i cant set property descriptors like wrtable except using Objkect.defineproperty (?) </p> <p>So what are the main benefits from using Object.create() to inherit from Objects vs Setting the prototypes and construcotrs ? =)</p> <p>3: Oh thx, yes thats def right thats not an extension of base object =) thx for the suggestion =)</p> <p>Thx for all the effort =)</p> <h3>Answer</h3> <p>Ok so when i do </p> <blockquote> <p>Nothing = {}</p> <p>base.prototype = Nothing;</p> </blockquote> <p>this doesnt prevent s.o to go up the prototype chain til Object.prototype ? if not , is there a way to do this ? =) Would ( Object.create(null); ) do this,</p> <p>and i thought that i had to set </p> <blockquote> <p>base.prototype.constructor = base;</p> </blockquote> <p>because otherwise, the prototypes constructor of</p> <blockquote> <p>var Top = new base();</p> </blockquote> <p>would be Nothings' or does'nt base inherit a constructor from somewhere up the prototype chain if the prototype is set to Nothing -> </p> <blockquote> <p>Top instanceof base // false </p> </blockquote> <h1>Update</h1> <p>I ended up doing it in a way like this now:</p> <pre><code>var base = { // a tiny little selfmade prototypical inheritance system // you are free to add function arguments for extending the created objects // neither instanceof nor .constructor is featured, because "classes" are no functions create: function(extension,desc) { // instances inherit from the proto objects var newInst = Object.create(this.proto, desc); if(this.proto.childExtendable) //if Subclass allows its Children to be Extendible, do so newInst.extend(extension); if(newInst.init||this.proto.init) //4 newInst.init() return newInst }, inherit: function(props) { // the "class" inherits static methods from the class var sub = Object.create(this); // and the proto objects inherits from the parent proto sub.proto = Object.create(this.proto); props.protect = this.protect; if(props.childExtendable) props.extend = this.extend; this.extend.call(sub.proto, props); return sub; }, extend: function (props) { for (var prop in props) { var propmatch = prop.match(/(.*?)__(.{1,5}?)__(.*)/)||["",prop,"",""]; this[propmatch[1]+propmatch[3]] = props[prop]; if(propmatch[2]) this.protect(propmatch[1]+propmatch[3],propmatch[2]); } }, protect: function(prop,flags) { //with each call it toggles the given flags, so you can protect funcitons given to the inherit function ;; //This should be available to all childs, but adding it to the base.proto, it changes Object.prototyppe ( therefore not a good idea) var d = Object.getOwnPropertyDescriptor(this, prop); if (flags.match(/w/)){ Ti.API.info("Setting writable for propertie " + prop + " in Object " + this + " to " + !d.writable); Object.defineProperty(this, prop, {writable:!d.writable});}; if (flags.match(/c/)){ Ti.API.info("Setting configurable for propertie " + prop + "in Object " + this); Object.defineProperty(this, prop, {configurable:!d.configurable});}; if (flags.match(/e/)){ Ti.API.info("Setting enumerable for propertie " + prop + "in Object " + this); Object.defineProperty(this, prop, {configurable:!d.enumerable});}; if (flags.match(/a/)){ Ti.API.info("Setting enumerable for propertie " + prop + "in Object " + this); Object.preventExtensions(this);}; }, init: function() {}, proto: Object.prototype // or null, if you want }; var Human = base.inherit({ //will be put in Human.proto childExtendable:true, init:function() {alert("Humans Init for all Instances")}, say:function() { alert("Hi, I'm "+this.name); } }); Human.proto.name = "default"; // You could use an argument to the inherit function // I just want to make clear what happens Ti.API.info(Object.getPrototypeOf(Function) + "a"); var paul = Human.create({ //extends this object name: "Paul", test: function() {alert("test")}, init__wce__: function() {alert("Pauls Own Init")}, say__w__ : function() { alert("Hi, I'm" + this.name + "s Own Function")} }); paul.name = "Paul"; // and again, the create function might do it for you paul.say = function() {alert("Pauls say is overwritten")} // define init without __wce__ and it will be overwritten paul.say(); // -&gt; "Hi, I'm Paul" </code></pre> <p>Just if anyone cares<br> However, jsfiddle won't run this, Titanium does everythign as expected maybe some strict mode (??) </p>
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