Rebuilding class instances from JSON data
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<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>Rebuilding class instances from JSON data</title>
<style type="text/css">
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body {
margin:0;
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</style>
<link rel="stylesheet" type="text/css" href="yui_2.7.0b-lib/fonts/fonts-min.css" />
<script type="text/javascript" src="yui_2.7.0b-lib/yahoo-dom-event/yahoo-dom-event.js"></script>
<script type="text/javascript" src="yui_2.7.0b-lib/json/json-min.js"></script>
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<style type="text/css">
#demo textarea {
background: #fff;
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padding: 1em;
width: 80%;
height: 50px;
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<body class=" yui-skin-sam">
<h1>Rebuilding class instances from JSON data</h1>
<div class="exampleIntro">
<p>This example illustrates one method of serializing and recreating class instances by using the <code>replacer</code> and <code>reviver</code> parameters to <code>JSON.stringify</code> and <code>JSON.parse</code> respectively.</p>
</div>
<!--BEGIN SOURCE CODE FOR EXAMPLE -->
<div id="demo">
<button type="button" id="demo_freeze">Freeze</button>
<button type="button" id="demo_thaw" disabled="disabled">Thaw</button>
<textarea id="demo_frozen">(stringify results here)</textarea>
<div id="demo_thawed"></div>
</div>
<script type="text/javascript">
YAHOO.util.Event.onDOMReady(function () {
var Event = YAHOO.util.Event,
Dom = YAHOO.util.Dom,
JSON = YAHOO.lang.JSON,
Demo;
Demo = YAHOO.namespace('demo').FreezeThaw = {
data : null,
jsonString : null,
cryo : function (k,o) {
return (o instanceof CaveMan) ? CaveMan.freeze(o) : o;
},
revive : function (k,v) {
// Turn anything that looks like a UTC date string into a Date instance
if (typeof v === 'string') {
return JSON.stringToDate(v);;
}
// Check for cavemen by the _class key
if (v instanceof Object && v._class == 'CaveMan') {
return CaveMan.thaw(v);
}
// default to returning the value unaltered
return v;
}
};
function CaveMan(name,discovered) {
this.name = name;
this.discovered = discovered;
};
CaveMan.prototype.getName = function () {
return this.name + ", the cave man";
}
// Static methods to convert to and from a basic object structure
CaveMan.thaw = function (o) {
return new CaveMan(o.n, o.d);
};
// Convert to a basic object structure including a class identifier
CaveMan.freeze = function (cm) {
return {
_class : 'CaveMan',
n : cm.name,
d : cm.discovered // remains a Date for standard JSON serialization
};
};
Demo.data = {
count : 1,
type : 'Hominid',
specimen : [
new CaveMan('Ed',new Date(1946,6,6))
]
};
Event.on('demo_freeze','click',function (e) {
Demo.jsonString = JSON.stringify(Demo.data, Demo.cryo);
Dom.get('demo_frozen').value = Demo.jsonString;
Dom.get('demo_thaw').disabled = false;
});
Event.on('demo_thaw','click',function (e) {
var parsedData = JSON.parse(Demo.jsonString, Demo.revive);
cm = parsedData.specimen[0];
Dom.get('demo_thawed').innerHTML =
"<p>Specimen count: " + parsedData.count + "</p>"+
"<p>Specimen type: " + parsedData.type + "</p>"+
"<p>Instanceof CaveMan: " + (cm instanceof CaveMan) + "</p>"+
"<p>Name: " + cm.getName() + "</p>"+
"<p>Discovered: " + cm.discovered + "</p>";
});
});
</script>
<!--END SOURCE CODE FOR EXAMPLE -->
</body>
</html>
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