你如何检查和放大器;变量在指令设置 [英] How do you check if & variable is set in directive

问题描述

在一个指令，在那里你通过ARG设置方法回调，说：

In a directive, where you set a method callback through an arg, say:

<my-directive callback='showAlert()' />

您可以通过检索的范围在返回设置变量：

You can retrieve the variable through the scope setting in the return:

scope: {
    callback: "&callback"
}

如果回调不设置，例如：

If the callback is not set, eg:

<my-directive />

$ scope.callback的值仍然是：

The value of $scope.callback is still:

$scope.callback():function (locals) {
    return parentGet(scope, locals);
}

有没有检查回调没有设置好办法？

Is there a good way to check that the callback was not set?

推荐答案

我能想到的一个方法是检查指令名称的属性参数，如

One way i can think off is to check the attribute parameter for the directive name like

link: function (scope, elm, attrs) {

   if(attrs.callback) {
       //this attribute has been defined.
   }

}

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