Ext.extend作为在Ext.base.js文件中作为继承扩展的方法进行使用。
它的基础代码为：
代码
extend : function(){
// inline overrides
var io = function(o){
for(var m in o){
this[m] = o[m];
}
};
var oc = Object.prototype.constructor;
return function(sb, sp, overrides){
if(typeof sp == 'object'){
overrides = sp;
sp = sb;
sb = overrides.constructor != oc ? overrides.constructor : function(){sp.apply(this, arguments);};
}
var F = function(){},
sbp,
spp = sp.prototype;
F.prototype = spp;
sbp = sb.prototype = new F();
sbp.constructor=sb;
sb.superclass=spp;
if(spp.constructor == oc){
spp.constructor=sp;
}
sb.override = function(o){
Ext.override(sb, o);
};
sbp.superclass = sbp.supr = (function(){
return spp;
});
sbp.override = io;
Ext.override(sb, overrides);
sb.extend = function(o){return Ext.extend(sb, o);};
return sb;
};
}(),
override : function(origclass, overrides){
if(overrides){
var p = origclass.prototype;
Ext.apply(p, overrides);
if(Ext.isIE && overrides.hasOwnProperty('toString')){
p.toString = overrides.toString;
}
}
}
// inline overrides
var io = function(o){
for(var m in o){
this[m] = o[m];
}
};
var oc = Object.prototype.constructor;
return function(sb, sp, overrides){
if(typeof sp == 'object'){
overrides = sp;
sp = sb;
sb = overrides.constructor != oc ? overrides.constructor : function(){sp.apply(this, arguments);};
}
var F = function(){},
sbp,
spp = sp.prototype;
F.prototype = spp;
sbp = sb.prototype = new F();
sbp.constructor=sb;
sb.superclass=spp;
if(spp.constructor == oc){
spp.constructor=sp;
}
sb.override = function(o){
Ext.override(sb, o);
};
sbp.superclass = sbp.supr = (function(){
return spp;
});
sbp.override = io;
Ext.override(sb, overrides);
sb.extend = function(o){return Ext.extend(sb, o);};
return sb;
};
}(),
override : function(origclass, overrides){
if(overrides){
var p = origclass.prototype;
Ext.apply(p, overrides);
if(Ext.isIE && overrides.hasOwnProperty('toString')){
p.toString = overrides.toString;
}
}
}
其中overrides的参数，作为一个JSON对象，最终将调用Ext.apply(p, overrides);apply主要用于为p扩展overrides属性。
在子类使用时需要使用SubClass.superclass.constructor.call(this,…);的方式，以便它的基类可以将构造函数赋值给子类。
我们来看一个例子，ext-all-debug.js中的Ext.state.CookieProvider，它是作为Cookie的提供类来使用的：
代码
Ext.state.CookieProvider = Ext.extend(Ext.state.Provider, {
constructor : function(config){
Ext.state.CookieProvider.superclass.constructor.call(this);
this.path = "/";
this.expires = new Date(new Date().getTime()+(1000*60*60*24*7));
this.domain = null;
this.secure = false;
Ext.apply(this, config);
this.state = this.readCookies();
},
set : function(name, value){
if(typeof value == "undefined" || value === null){
this.clear(name);
return;
}
this.setCookie(name, value);
Ext.state.CookieProvider.superclass.set.call(this, name, value);
},
clear : function(name){
this.clearCookie(name);
Ext.state.CookieProvider.superclass.clear.call(this, name);
},
readCookies : function(){
var cookies = {},
c = document.cookie + ";",
re = /\s?(.*?)=(.*?);/g,
matches,
name,
value;
while((matches = re.exec(c)) != null){
name = matches[1];
value = matches[2];
if(name && name.substring(0,3) == "ys-"){
cookies[name.substr(3)] = this.decodeValue(value);
}
}
return cookies;
},
setCookie : function(name, value){
document.cookie = "ys-"+ name + "=" + this.encodeValue(value) +
((this.expires == null) ? "" : ("; expires=" + this.expires.toGMTString())) +
((this.path == null) ? "" : ("; path=" + this.path)) +
((this.domain == null) ? "" : ("; domain=" + this.domain)) +
((this.secure == true) ? "; secure" : "");
},
clearCookie : function(name){
document.cookie = "ys-" + name + "=null; expires=Thu, 01-Jan-70 00:00:01 GMT" +
((this.path == null) ? "" : ("; path=" + this.path)) +
((this.domain == null) ? "" : ("; domain=" + this.domain)) +
((this.secure == true) ? "; secure" : "");
}
});
constructor : function(config){
Ext.state.CookieProvider.superclass.constructor.call(this);
this.path = "/";
this.expires = new Date(new Date().getTime()+(1000*60*60*24*7));
this.domain = null;
this.secure = false;
Ext.apply(this, config);
this.state = this.readCookies();
},
set : function(name, value){
if(typeof value == "undefined" || value === null){
this.clear(name);
return;
}
this.setCookie(name, value);
Ext.state.CookieProvider.superclass.set.call(this, name, value);
},
clear : function(name){
this.clearCookie(name);
Ext.state.CookieProvider.superclass.clear.call(this, name);
},
readCookies : function(){
var cookies = {},
c = document.cookie + ";",
re = /\s?(.*?)=(.*?);/g,
matches,
name,
value;
while((matches = re.exec(c)) != null){
name = matches[1];
value = matches[2];
if(name && name.substring(0,3) == "ys-"){
cookies[name.substr(3)] = this.decodeValue(value);
}
}
return cookies;
},
setCookie : function(name, value){
document.cookie = "ys-"+ name + "=" + this.encodeValue(value) +
((this.expires == null) ? "" : ("; expires=" + this.expires.toGMTString())) +
((this.path == null) ? "" : ("; path=" + this.path)) +
((this.domain == null) ? "" : ("; domain=" + this.domain)) +
((this.secure == true) ? "; secure" : "");
},
clearCookie : function(name){
document.cookie = "ys-" + name + "=null; expires=Thu, 01-Jan-70 00:00:01 GMT" +
((this.path == null) ? "" : ("; path=" + this.path)) +
((this.domain == null) ? "" : ("; domain=" + this.domain)) +
((this.secure == true) ? "; secure" : "");
}
});
Ext.state.Provider是作为超类来使用，它是页面层面上的缓存。
它的应用：
Ext.state.Manager.setProvider(new Ext.state.CookieProvider());
