如何 $watch 指令中的多个内插属性? [英] How do I $watch multiple interpolated attributes in a directive?

问题描述

我不明白如何在链接函数中同时观察多个属性，所以我创建了一个包含所有参数的对象并观察它.但我注意到链接函数中的属性是一个字符串而不是一个对象，所以我使用的是 angular.fromJson(val).

I don't understand how to watch multiple attributes at the same time in the link function, so I create an object with all the parameters and I watch for it. But I noticed that the attribute in the link function is a string and not an object so I'm using angular.fromJson(val).

我发现的所有示例都只使用一个参数

您能解释一下如何查看多个属性吗?

Could you explain how to watch multiple attributes?

谢谢

编辑:我不能使用 attrs 参数，因为我需要绑定属性——即，它们需要插值.例如

EDIT: I cannot use attrs parameter because I need to bind the attributes -- i.e., they require interpolation. For example

<ul class="thumbnails">
    <li class="span3" ng-repeat="image in currentSizeInfo.images" >
       <upload-file info = "{{getInfo($index)}}" foo="foo$index" ></upload-file>
    </li>
</ul>

我认为我必须使用 $watch

I think that I have to use $watch

link:function (scope, element, attrs ) {
    scope.$watch('info', function (val) {
    // if info is and foo is .... do all the stuff
    })
}

推荐答案

我不确定我是否完全理解你的问题，所以如果我误解了请纠正我.只是想从指令的多个属性中提取值吗?假设您有这样的 HTML:

I'm not sure I fully understand your question, so please correct me if I misunderstand. Are just want to pull values from multiple attributes on your directive? So say you have a HTML like this:

<my-directive attr1="data1" attr2="data2" attr3="data3" />

您想获得这些不同属性的值吗?在链接函数中，您只需使用 attrs 参数.例如:

And you want to get the values of those different attributes? In the link function, you just use the attrs parameter. For example:

link: function(scope, element, attrs) {
    var foo1 = attrs.attr1;
    var foo2 = attrs.attr2;
    var foo3 = attrs.attr3;
}

您还可以使用指令上的 scope 属性自动将属性绑定到您的作用域.请参阅关于指令的他们的文档.所以，像这样:

You can also use the scope property on the directive to automatically bind attributes to your scope. See their documentation on directives. So, something like this:

scope: {
    attr1: '@',
    attr2: '@',
    attr3: '@'
}

然后这些属性会自动进入您的范围.但是，我发现，这些值并不总是在您期望的范围内.所以你可以使用 $watch 函数来做你需要的事情.类似的东西:

And then those properties end up in your scope automatically. However, as I found out, those values aren't always in the scope when you'd expect. So you can use the $watch function to do what you need with them. Something like:

link: function(scope, element, attrs) {
    scope.$watch("attr1", function () {
         if (scope.attr1)
         {
              //stuff with attr1
         }
    }
    scope.$watch("attr2", function () {
         if (scope.attr2)
         {
              //stuff with attr2
         }
    }
    //....
}

如果您需要同时使用它们，您可以对 $watch 的第一个参数使用一个函数，该函数返回一个字符串，一旦它们都存在并且然后将您的逻辑放在作为第二个参数的函数中.所以是这样的:

If you need to use them all together at the same time, you could use a function for the first parameter of the $watch that returns a string that would be different once they are all there and then put your logic in the function that is the 2nd parameter. So something like this:

link: function(scope, element, attrs) {
    scope.$watch(function () {
        if (scope.attr1 && scope.attr2 && scope.attr3)
        {
            return "allSet";
        }
        else
        {
            return "";
        }
    }, function (newVal) {
        if ("allSet" == newVal)
        {
            //do stuff with all the properties
        }
    });
}

如果您想将对象绑定到您的作用域中，您可以使用="而不是@".另一个选项是&"它评估父作用域中的函数.这一切都在上面链接的指令文档中进行了解释.

If you're wanting to bind objects into your scope, you can use '=' instead of '@'. Another option is '&' which evaluates a function in the parent scope. This is all explained in the directive documentation linked above.

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