问题描述
在大多数样品含有使用code为NG-文件上传的小提琴的（）就像一个在（），上传回复回调函数的包裹code在 $超时服务电话的，但这些电话中没有通过的任何延迟参数
In most of the fiddles containing sample usage code for ng-file-upload (https://github.com/danialfarid/ng-file-upload) like the one at (http://jsfiddle.net/danialfarid/maqbzv15/1118/), the upload response callback functions wrap their code in a $timeout service call, but these calls do not have any delay parameter passed in.
该Angular.js文档为 $超时（ $超时）表示，延迟是可选的，但你为什么要做出 $通话超时，如果不耽误code正在运行。换句话说，而不是下面，为什么不这样做一前一后：
The Angular.js docs for $timeout (https://docs.angularjs.org/api/ng/service/$timeout) indicate that the delay is optional, but why would you want to make a call to $timeout if not to delay the code being run. In other words instead of the following, why not do the one after:
//inject angular file upload directives and services.
var app = angular.module('fileUpload', ['ngFileUpload']);
app.controller('MyCtrl', ['$scope', 'Upload', '$timeout', function ($scope, Upload, $timeout) {
$scope.uploadPic = function(file) {
file.upload = Upload.upload({
url: 'https://angular-file-upload-cors-srv.appspot.com/upload',
data: {username: $scope.username, file: file},
});
file.upload.then(function (response) {
$timeout(function () {
file.result = response.data;
});
}, function (response) {
if (response.status > 0)
$scope.errorMsg = response.status + ': ' + response.data;
}, function (evt) {
// Math.min is to fix IE which reports 200% sometimes
file.progress = Math.min(100, parseInt(100.0 * evt.loaded / evt.total));
});
}
}]);
有什么理由 $超时包装在所有这些例子呢？将在该位置以下file.upload呼叫工作：
Is there any reason for the $timeout wrapper in all these examples? Would the following file.upload call work in its place?:
file.upload.then(function (response) {
file.result = response.data;
}, function (response) {
if (response.status > 0)
$scope.errorMsg = response.status + ': ' + response.data;
}, function (evt) {
// Math.min is to fix IE which reports 200% sometimes
file.progress = Math.min(100, parseInt(100.0 * evt.loaded / evt.total));
});
编辑：我可以看到，它似乎没有 $超时包装运行，但它包含在所有的例子其实让我觉得这是故意的，这可能意味着有一个安全/健壮性/浏览器的兼容性优势的情况下，我不明白这里。
I can see that it appears to run without the $timeout wrapper, but the fact it's included in all the examples makes me think it's deliberate, which probably means there's a security/robustness/browser compatibility edge case I don't understand here.
推荐答案
这是所有做与角的消化周期。我会尽力我继续解释摘要周期是与前一个例子来证明这一点。想象一下以下code：
It's all to do with Angular's digest cycle. I'll try to demonstrate this with an example before I go on to explain what the digest cycle is. Imagine the following code:
angular.module('app', []).controller('TestController', ['$scope', function($scope){
$scope.name = 'Tom';
setTimeout(function(){
$scope.name = 'Bob';
}, 2000);
}]);
有与此code的固有问题。正如我们改变 $ scope.name 的变量2秒后，角完全不知道这种变化 $ scope.name 。如果你现在考虑下面的例子中，我们使用 $超时而不是：
There's an inherent problem with this code. As much as we change the variable of $scope.name after 2 seconds, Angular is completely unaware of this change to $scope.name. If you now consider the following example where we use $timeout instead:
angular.module('app', []).controller('TestController', ['$scope', '$timeout', function($scope, $timeout){
$scope.name = 'Tom';
$timeout(function(){
$scope.name = 'Bob';
}, 2000);
}]);
角将调用匿名函数两秒钟之后，然而，它随后将开始角度的消化周期。这是 $超时和setTimeout的，消化周期正在运行。
Angular will call the anonymous function after two seconds, however, it will then start off Angular's digest cycle. This is the main difference between $timeout and setTimeout, the digest cycle being run.
摘要周期（简单地说）角去了所有的观察者（绑定）的，检查任何更改并重新渲染的地方不合适。你可能已经看到了提至 $ $范围适用其他地方 - 。这是怎么开始的消化周期
The digest cycle is (put simply) Angular going over all of the watchers (bindings), checking for any changes and re-rendering where appropiate. You may have seen a mention to $scope.$apply elsewhere - this is how to start the digest cycle.
至于您所提供的例子：如果没有使用 $超时，角也不会知道，任何已经作了修改，因此，您的视图不会更新。我提到 $范围。$适用较早所以你可能会奇怪，为什么我们不只是用这个来代替？使用$范围的问题。$应用是，你不能确保摘要周期是不是已经在进行中。如果你调用它，而一个occcuring，你会看到一个错误 $消化正在进行中。 $超时只会在当前周期之后运行，因此，不会发生这个错误。
With regards to the example you provided: If the $timeout wasn't used, Angular wouldn't be aware that any changes have been made and as such, your view wouldn't update. I mentioned $scope.$apply earlier so you may be wondering why we don't just use this instead? The problem with using $scope.$apply is that you cannot be sure that a digest cycle isn't in progress already. If you do call it while one is occcuring, you'll see an error "$digest is already in progress". $timeout will only run after the current cycle and as such, this error won't happen.
人们通常使用 $超时没有任何延迟通知角的变化已经由第三方做出（像你的文件上传），这否则不会知道发生了什么。
People often use $timeout without any delay to notify Angular that a change has been made by a third party (like your file uploader), that it otherwise wouldn't know had happened.
希望这将清除的东西了。
Hopefully this clears things up.
汤姆
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