在《AngularJS权威教程》中，自定义指令和DOM双向数据绑定有一个在线demo，网址：http://jsbin.com/IteNita/1/edit?html,js,output，具体代码如下：
<!doctype html>
<html ng-app="myApp">
<head>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.0-rc.3/angular.js"></script>
</head>
<body> <label>Their URL field:</label>
<input type="text" ng-model="theirUrl">
<div my-directive
some-attr="theirUrl"
my-link-text="Click me to go to Google"></div> <script>
angular.module('myApp', [])
.directive('myDirective', function() {
return {
restrict: 'A',
replace: true,
scope: {
myUrl: '=someAttr',
myLinkText: '@'
},
template: '\
<div>\
<label>My Url Field:</label>\
<input type="text" ng-model="myUrl" />\
<a href="{{myUrl}}">{{myLinkText}}</a>\
</div>\
'
}
})
</script> </body>
</html>
其中myUrl: '=someAttr'我不是很理解，于是改成 myUrl: '@someAttr',但是这样页面显示如图：
aaarticlea/png;base64,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" alt="" />
查看元素发现链接的href="theirUrl",并且；两个输入框的内容也不同步，仔细查看代码，发现DOM中将some-attr设置值方式不是表达式，所以修改如下（修改处为绿色）：
<body> <label>Their URL field:</label>
<input type="text" ng-model="theirUrl">
<div my-directive
some-attr={{theirUrl}}
my-link-text="Click me to go to Google"></div> <script>
angular.module('myApp', [])
.directive('myDirective', function() {
return {
restrict: 'A',
replace: true,
scope: {
myUrl: '@someAttr',
myLinkText: '@'
},
template: '\
<div>\
<label>My Url Field:</label>\
<input type="text" ng-model="myUrl" />\
<a href="{{myUrl}}">{{myLinkText}}</a>\
</div>\
'
}
})
</script> </body>
效果是，第2个输入框随着第1个变化，反之不是。
总结：指令要访问其内部的指令，需要：
1.指令属性值用表达式即{{}}设置，改为“”
2.内部指令对应属性数据绑定”@”改为”=”