如何检查指令的方法参数是否在 AngularJS 中指定? [英] How to check if a method argument of a directive is specified in AngularJS?
问题描述
我创建了一个包含按钮的自定义指令.此按钮从回调"属性指定的父范围调用方法.
I've created a custom directive which contains a button. This button calls a method from parent scope specified by 'callback' attribute.
<!DOCTYPE html>
<html ng-app="app">
<head>
<title>Simple directive</title>
<script src="js/lib/angular/angular.js"></script>
<script type="text/javascript">
var app = angular.module('app', []);
app.controller('TestController', function($scope) {
$scope.doSomething = function(param) {
alert('Something called with: ' + param);
}
})
app.directive('myDirective', function() {
var ret = {
restrict: 'E',
scope: {
user: '@',
callback: '&' // bound a function from the scope
},
template: '<div>Hello {{user}}<button ng-show="hasCallback()" ng-click="callback({userData: user})">Callback</button>',
controller: function($scope) {
$scope.hasCallback2 = function() {
var t = typeof $scope.callback;
return t == 'function';
}
$scope.hasCallback = function() {
return angular.isDefined($scope.callback);
}
}
};
return ret;
});
</script>
</head>
<body ng-controller="TestController">
<my-directive user="cat" callback="doSomething(userData)"></my-directive>
<my-directive user="dog" callback="doSomething(userData)"></my-directive>
<my-directive user="pig"></my-directive>
</body>
</html>
我的问题是:
如何控制模板内按钮的可见性?如果自定义标记中未指定回调属性，我想隐藏它(请参阅第三个 my-directive 标记).当我检查回调的 typeof 时，我总是得到 'function' 并且 angular.isDefined(...) 也返回 true.
How can I control visibility of button inside template? I'd like to hide it if callback attribute not specified in custom tag (see 3rd my-directive tag). When I check typeof of callback, I always get 'function' and angular.isDefined(...) also returns true.
推荐答案
使用 '&?'如果尚未设置该属性，则返回 undefined.
Using '&?' returns undefined if the attribute has not been set.
'&'= 始终定义回调函数.
'&' = callback function is defined always.
'&?'= 只有在 html 模板中定义了属性时才定义回调函数.
'&?' = callback function is defined only when attribute is defined in html template.
bindToController: {
callback: '&?'
},
controller: function() {
if (this.callback === undefined) {
// attribute "callback" was not defined
}
}
注意:适用于 Angular 1.4.8.我不确定它是否适用于旧版本.
Note: Works in Angular 1.4.8. I'm not sure if it works in older versions.
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