Ext.
extend方法是用来实现类的继承。
extend(Object subclass,Object superclass,[Object overrides] : Object
第一个参数：子类
第二个参数：父类
第三个参数：要覆盖的属性。
这里需要强调一下，子类继承下来的是父类中通过superclass.prototype方式定义的属性（包括用此方法定义的函数）。
例子如下：
Js代码
<script type=
"text/javascript">
function S(){ } S.prototype.s =
"s"; S.prototype.s1 =
"s1";
function C(){
this.c =
"c";
this.c1 =
"c1"; }
Ext.
extend(C,S,{s1:
"by c overload"});
var c =
new C(); alert(c.s); alert(c.s1); </script>
<script type="text/javascript">
function S(){
}
S.prototype.s = "s";
S.prototype.s1 = "s1";
function C(){
this.c = "c";
this.c1 = "c1";
}
Ext.
extend(C,S,{s1:"by c overload"});
var c = new C();
alert(c.s); //s
alert(c.s1); //by c overload
</script>
如果按下面这个方式写就会提示c.s没有定义(undefind)：
Js代码
<script type=
"text/javascript">
function S(){
this.s =
"s";
this.s1 =
"s1"; }
function C(){
this.c =
"c";
this.c1 =
"c1"; }
Ext.
extend(C,S,{s1:
"by c overload"});
var c =
new C(); alert(c.s); alert(c.s1); </script>
<script type="text/javascript">
function S(){
this.s = "s";
this.s1 = "s1";
}
function C(){
this.c = "c";
this.c1 = "c1";
}
Ext.
extend(C,S,{s1:"by c overload"});
var c = new C();
alert(c.s); //undefind
alert(c.s1); //by c overload
</script>
也可以通过如下方式来实现类的继承
Js代码
<script type=
"text/javascript">
function S(){ } S.prototype.s =
"s"; S.prototype.s1 =
"s1"; C =
Ext.
extend(S,{s1:
"by c overload"});
var c =
new C(); alert(c.s); alert(c.s1); </script>
<script type="text/javascript">
function S(){
}
S.prototype.s = "s";
S.prototype.s1 = "s1";
C =
Ext.
extend(S,{s1:"by c overload"});
var c = new C();
alert(c.s); //s
alert(c.s1); //by c overload
</script>
此时，C是子类，S是父类
相关资源：敏捷开发V1.0.pptx
