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AngularJS的ng-repeat指令与scope继承关系实例详解

更新时间:2020-04-21 00:10:24 作者:startmvc
本文实例分析了AngularJS的ng-repeat指令与scope继承关系。分享给大家供大家参考,具体如下:n

本文实例分析了AngularJS的ng-repeat指令与scope继承关系。分享给大家供大家参考,具体如下:

ng-repeat指令的使用方式可以参考如下代码:


<!doctype html>
<html lang="en">
 <head>
 <meta charset="utf-8">
 <title>ng-repeat</title>
 <script src="jquery-1.11.1.js"></script>
 <script src="angular-1.2.25.js"></script>
 <script>
 function wholeController($scope,$rootScope,$injector)
 {
 $scope.buttons = ["button1","button2","button3"];
 $scope.btnFunc = function(value){
 alert(value);
 };
 }
 </script>
 </head>
 <body ng-app>
 <div id="first" ng-controller="wholeController">
 <div id="buttonDiv">
 <input type="button" ng-repeat="button in buttons" id="btn{{$index}}" value="{{button}}" ng-click="btnFunc(button);"/>
 </div>
 <input type="button" value="test" ng-click="testFunc();">
 </div>
 </body>
</html>

这里需要注意:ng-click中访问button不需要使用{{button}}这种语法;而其他非AngularJS环境下,必须通过{{button}}这种方式取值。ng-repeat指令中$index代表遍历的数组的索引,从0开始。

我们知道ng-controller指令会创建一个新的作用域scope,测试代码如下:


<!doctype html>
<html lang="en">
 <head>
 <meta charset="utf-8">
 <title>ng-repeat</title>
 <script src="jquery-1.11.1.js"></script>
 <script src="angular-1.2.25.js"></script>
 <script>
 //$scope是ng-controller指令新建的作用域
 function wholeController($scope,$rootScope,$injector)
 {
 alert($scope.$parent === $rootScope);//输出true
 }
 </script>
 </head>
 <body ng-app>
 <div id="first" ng-controller="wholeController">
 </div>
 </body>
</html>

我们可以使用angular.element(domElement).scope()方法来获得某一个DOM元素相关联的作用域。


<!doctype html>
<html lang="en">
 <head>
 <meta charset="utf-8">
 <title>ng-repeat</title>
 <script src="jquery-1.11.1.js"></script>
 <script src="angular-1.2.25.js"></script>
 <script>
 function wholeController($scope,$rootScope,$injector)
 {
 $scope.buttons = ["button1","button2","button3"];
 $scope.testFunc = function(){
 //拿到dom元素上关联的作用域
 var scope0 = angular.element($("#btn0")[0]).scope();
 var scope1 = angular.element($("#btn1")[0]).scope();
 alert(scope0 == scope1);//输出false
 alert(scope0.$parent === $scope);//true
 alert(scope1.$parent === $scope);//true
 };
 }
 </script>
 </head>
 <body ng-app>
 <div id="first" ng-controller="wholeController">
 <div id="buttonDiv">
 <input type="button" ng-repeat="button in buttons" id="btn{{$index}}" value="{{button}}" />
 </div>
 <input type="button" value="test" ng-click="testFunc();">
 </div>
 </body>
</html>

可以看到ng-repeat指令会新建作用域,而且是为循环中的每个dom元素新建一个作用域。通过F12调试,可以看到scope0和scope1的内容如下:

可以看到scope0和scope1中都有一个buttons属性,这个属性就是从父作用域下继承得到的,很类似于JavaScript的原型链。


<!doctype html>
<html lang="en">
 <head>
 <meta charset="utf-8">
 <title>ng-repeat</title>
 <script src="jquery-1.11.1.js"></script>
 <script src="angular-1.2.25.js"></script>
 <script>
 function wholeController($scope,$rootScope,$injector)
 {
 $scope.buttons = ["button1","button2","button3"];
 $scope.method1 = function(){
 var scope0 = angular.element($("#btn0")[0]).scope();
 scope0.buttons = ["a1","b1","c1"];
 };
 $scope.method2 = function(){
 var scope0 = angular.element($("#btn0")[0]).scope();
 scope0.$parent.buttons = ["a2","b2","c2"];
 };
 $scope.method3 = function(){
 var scope0 = angular.element($("#btn0")[0]).scope();
 scope0.buttons[0] = "a3";
 scope0.buttons[1] = "b3";
 scope0.buttons[2] = "c3";
 };
 }
 </script>
 </head>
 <body ng-app>
 <div id="first" ng-controller="wholeController">
 <div id="buttonDiv">
 <input type="button" ng-repeat="button in buttons" id="btn{{$index}}" value="{{button}}" />
 </div>
 <input type="button" value="method1" ng-click="method1();">
 <input type="button" value="method2" ng-click="method2();">
 <input type="button" value="method3" ng-click="method3();">
 </div>
 </body>
</html>

当点击method1、method2、method3的时候,我们希望将按钮button1、button2、button3替换掉。运行上面的代码可以发现:method2和method3都能成功达到目的,但是method1不能达到目的。这其实很类似C语言中传值,还是传引用的问题。


var obj = {"name":"aty"};
wrongChangeName(obj);
alert(obj.name);//仍然是aty
rightChangeName(obj);
alert(obj.name);//hehe
function rightChangeName(obj)
{
 obj.name="hehe";
}
function wrongChangeName(obj)
{
 obj = {"name":"hehe"};
}

wrongChangeName就类似于我们上面的method1,而rightChangeName类似于上面的method3。也就是说如果我们想在childScope中修改parentScope中某个属性的值,那么该属性一定不能是javascript基本数据类型,一定要是对象类型。而且不能直接通过=进行赋值修改,必须是调用对象的方法来修改。

AngularJS ng-repeat指令 scope 继承