如何获得角$间隔的状态 - 检查间隔已被取消或不 [英] How to get the status of angular $interval - check if the interval has been cancelled or not

问题描述

我是新来的角（和JS），只是有点糊涂了。

I am new to Angular (and JS) and just a little confused.

我开始一个定时器：

var getOverviewMapTimer = $interval($scope.UpdateOverviewMap, UPDATE_FREQUENCY); 

和，如果我的理解是， getOverviewMapTimer 是一个承诺。

and, if I understand it, getOverviewMapTimer is a "promise".

我希望能够检查是否定时器运行和放大器;原本希望如果我永远结果
$ interval.cancel（getOverviewMapTimer）; 然后 getOverviewMapTimer 是空我可以检查这一点。

I want to be able to check if the timer is running & had excepted that if I ever
$interval.cancel(getOverviewMapTimer); then getOverviewMapTimer would be null and I could check for that.

这似乎不是如此。

我必须明确地摧毁承诺（咕什么是定时器的承诺已经被取消了？）。？如果是这样，如何​​与放大器;我会那么必须显式地将它设置为空？

Do I have to explicitly destroy the promise (what goo is a promise to timer that has been cancelled?).? If so, how & would I then have to explicitly set it to null?

我的认为的我应该用取消（getOverviewMapTimer）; ，但我不是100％确定为 getOverviewMapTimer 还是非空之后。

I think that I should use cancel(getOverviewMapTimer);, but am not 100% sure as getOverviewMapTimer is still non-null afterwards.

感谢您的帮助。

推荐答案

VAR getOverviewMapTimer = $间隔（...）后; getOverviewMapTimer 持有一个对象的引用（恰好是一个承诺）。

After var getOverviewMapTimer = $interval(...); getOverviewMapTimer holds a reference to an object (that happens to be a promise).

做 $ interval.cancel（getOverviewMapTimer）通过（并取消）由 getOverviewMapTimer 变量引用的对象，但有没有办法将对象转换为空。在 getOverviewMapTimer 变量将继续持有的承诺目标，并把它设置为null的唯一途径一提的是，通过一项新的任务（即明确地将其设置为null）：​​

Doing $interval.cancel(getOverviewMapTimer) passes (and cancels) the object referenced by the getOverviewMapTimer variable, but there is no way to convert an object to null. The getOverviewMapTimer variable will continue to hold a reference to the promise object and the only way to set it to null is through a new assignment (i.e. explicitely setting it to null):

var getOverviewMapTimer = $interval(...);
...
$interval.cancel(getOverviewMapTimer);
getOverviewMapTimer = null;

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高级主题：

这听起来的确是好的，有一个简单的方法，以找出是否一个区间的承诺已被取消或没有（如添加自定义取消属性的承诺对象取消区间）时，其值设置为true。结果
角是不够冷静，是令人难以置信的灵活性和可扩展性，因此使用 服务装饰的概念 ，我们能够增强的 $间隔服务，延长其取消（）方法添加取消属性并将其值设置为真正取消的区间时的承诺：

It sounds indeed nice to have an easy way to find out if an interval-promise has been cancelled or not (e.g. adding a custom cancelled property to the promise object and setting its value to true when cancelling the interval).
Angular is cool enough to be incredibly flexible and extensible, so using the concept of a Service Decorator we are able to "augment" the $interval service, extending its cancel() method to add a cancelled property and setting its value to true when cancelling an interval-promise:

/* Service Decorators can be configured in `config` blocks */
app.config(function ($provide) {

    /* Register a decorator for the `$interval` service */
    $provide.decorator('$interval', function ($delegate) {

        /* Keep a reference to the original `cancel()` method */
        var originalCancel = $delegate.cancel;

        /* Define a new `cancel()` method */
        $delegate.cancel = function (intervalPromise) {

            /* First, call the original `cancel()` method */
            var retValue = originalCancel(intervalPromise);

            /* If the promise has been successfully cancelled,
             * add a `cancelled` property (with value `true`) */
            if (retValue && intervalPromise) {
                intervalPromise.cancelled = true;
            }

            /* Return the value returned by the original method */
            return retValue;
        };

        /* Return the original (but "augmented") service */
        return $delegate;
    });
});

现在，我们可以使用 $间隔服务和往常一样，我们可以随时检查的间隔，承诺的取消属性来找出它是否已被取消。

Now, we can use the $interval service as usual and we can always check an interval-promise's cancelled property to find out if it has been cancelled.

var getOverviewMapTimer = $interval(...);
...
console.log(!!getOverviewMapTimer.cancelled);   // false
$interval.cancel(getOverviewMapTimer);
console.log(!!getOverviewMapTimer.cancelled);   // true

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又见这个 短演示

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See, also, this short demo.

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