I'm finding that I need to update my page to my scope manually more and more since building an application in angular.
The only way I know of to do this is to call $apply() from the scope of my controllers and directives. The problem with this is that it keeps throwing an error to the console that reads :
Error: $digest already in progress
Does anyone know how to avoid this error or achieve the same thing but in a different way?
Don't use this pattern - This will end up causing more errors than it solves. Even though you think it fixed something, it didn't.
You can check if a $digest is already in progress by checking $scope.$$phase.
if(!$scope.$$phase) {
//$digest or $apply
}
$scope.$$phase will return "$digest" or "$apply" if a $digest or $apply is in progress. I believe the difference between these states is that $digest will process the watches of the current scope and its children, and $apply will process the watchers of all scopes.
To @dnc253's point, if you find yourself calling $digest or $apply frequently, you may be doing it wrong. I generally find I need to digest when I need to update the scope's state as a result of a DOM event firing outside the reach of Angular. For example, when a twitter bootstrap modal becomes hidden. Sometimes the DOM event fires when a $digest is in progress, sometimes not. That's why I use this check.
I would love to know a better way if anyone knows one.
From comments: by @anddoutoi
- Don't do
if (!$scope.$$phase) $scope.$apply(), it means your$scope.$apply()isn't high enough in the call stack.
if (!$scope.$$phase) $scope.$apply()", github.com/angular/angular.js/wiki/Anti-Patterns –
Petromilli $$ methods –
Gambrel evalAsync not do what you want? –
Guildsman From a recent discussion with the Angular guys on this very topic: For future-proofing reasons, you should not use $$phase
When pressed for the "right" way to do it, the answer is currently
$timeout(function() {
// anything you want can go here and will safely be run on the next digest.
})
I recently ran into this when writing angular services to wrap the facebook, google, and twitter APIs which, to varying degrees, have callbacks handed in.
Here's an example from within a service. (For the sake of brevity, the rest of the service -- that set up variables, injected $timeout etc. -- has been left off.)
window.gapi.client.load('oauth2', 'v2', function() {
var request = window.gapi.client.oauth2.userinfo.get();
request.execute(function(response) {
// This happens outside of angular land, so wrap it in a timeout
// with an implied apply and blammo, we're in action.
$timeout(function() {
if(typeof(response['error']) !== 'undefined'){
// If the google api sent us an error, reject the promise.
deferred.reject(response);
}else{
// Resolve the promise with the whole response if ok.
deferred.resolve(response);
}
});
});
});
Note that the delay argument for $timeout is optional and will default to 0 if left unset ($timeout calls $browser.defer which defaults to 0 if delay isn't set)
A little non-intuitive, but that's the answer from the guys writing Angular, so it's good enough for me!
$timeout rather than native setTimeout, why do you not use $window instead of the native window? –
Kerrison $timeout in this case, is that $timeout ensures that the angular scope is updated properly. If a $digest is not in progress, it will cause a new $digest to run. –
Golconda var myTimer =$timeout(function(){/*code to execute here*/ $timeout.cancel(myTimer); }) –
Chivalrous cancel it. From the docs: "As a result of this, the promise will be resolved with a rejection." You can't resolve a resolved promise. Your cancellation won't cause any errors, but it won't do anything positive either. –
Goods Don't use this pattern - This will end up causing more errors than it solves. Even though you think it fixed something, it didn't.
You can check if a $digest is already in progress by checking $scope.$$phase.
if(!$scope.$$phase) {
//$digest or $apply
}
$scope.$$phase will return "$digest" or "$apply" if a $digest or $apply is in progress. I believe the difference between these states is that $digest will process the watches of the current scope and its children, and $apply will process the watchers of all scopes.
To @dnc253's point, if you find yourself calling $digest or $apply frequently, you may be doing it wrong. I generally find I need to digest when I need to update the scope's state as a result of a DOM event firing outside the reach of Angular. For example, when a twitter bootstrap modal becomes hidden. Sometimes the DOM event fires when a $digest is in progress, sometimes not. That's why I use this check.
I would love to know a better way if anyone knows one.
From comments: by @anddoutoi
- Don't do
if (!$scope.$$phase) $scope.$apply(), it means your$scope.$apply()isn't high enough in the call stack.
if (!$scope.$$phase) $scope.$apply()", github.com/angular/angular.js/wiki/Anti-Patterns –
Petromilli $$ methods –
Gambrel evalAsync not do what you want? –
Guildsman The digest cycle is a synchronous call. It won't yield control to the browser's event loop until it is done. There are a few ways to deal with this. The easiest way to deal with this is to use the built in $timeout, and a second way is if you are using underscore or lodash (and you should be), call the following:
$timeout(function(){
//any code in here will automatically have an apply run afterwards
});
or if you have lodash:
_.defer(function(){$scope.$apply();});
We tried several workarounds, and we hated injecting $rootScope into all of our controllers, directives, and even some factories. So, the $timeout and _.defer have been our favorite so far. These methods successfully tell angular to wait until the next animation loop, which will guarantee that the current scope.$apply is over.
underscore.js. This solution isn't worth importing the entire underscore library just to use its defer function. I much prefer the $timeout solution because everyone already has access to $timeout through angular, without any dependencies on other libraries. –
Maurist if (!$rootScope.$$phase) with _.defer() in a directive, but this seems not to work in my situation. The directive makes a css transition, through jQuery.animate() and writes the width and height back into the scope during the animation steps. With scope.$$phase I have always a width and height value in the scope (a chart directive requires these values and throws an error, if they are not set), with _.defer() they seem to be set too late. I haven't analyzed it deeper, but in my situation $rootScope.$$phase works, while _.defer() doesn't. –
Blasius _.defer($scope.$apply);. Frankly I'm still not sure why not... :-/ –
Newspaper $apply in context of the window, not of the $scope. This would have worked: _.defer($scope.$apply.bind($scope)), cause you are binding the context of $apply to be $scope. –
Mien $timeout otherwise it will give error.stackoverflow.com/a/19009389 –
Visitation _.defer(function(){$scope.$apply();}); between each other fixed the error. –
Foothill Many of the answers here contain good advices but can also lead to confusion. Simply using $timeout is not the best nor the right solution.
Also, be sure to read that if you are concerned by performances or scalability.
$$phase is private to the framework and there are good reasons for that.
$timeout(callback) will wait until the current digest cycle (if any) is done, then execute the callback, then run at the end a full $apply.
$timeout(callback, delay, false) will do the same (with an optional delay before executing the callback), but will not fire an $apply (third argument) which saves performances if you didn't modify your Angular model ($scope).
$scope.$apply(callback) invokes, among other things, $rootScope.$digest, which means it will redigest the root scope of the application and all of its children, even if you're within an isolated scope.
$scope.$digest() will simply sync its model to the view, but will not digest its parents scope, which can save a lot of performances when working on an isolated part of your HTML with an isolated scope (from a directive mostly). $digest does not take a callback: you execute the code, then digest.
$scope.$evalAsync(callback) has been introduced with angularjs 1.2, and will probably solve most of your troubles. Please refer to the last paragraph to learn more about it.
if you get the $digest already in progress error, then your architecture is wrong: either you don't need to redigest your scope, or you should not be in charge of that (see below).
When you get that error, you're trying to digest your scope while it's already in progress: since you don't know the state of your scope at that point, you're not in charge of dealing with its digestion.
function editModel() {
$scope.someVar = someVal;
/* Do not apply your scope here since we don't know if that
function is called synchronously from Angular or from an
asynchronous code */
}
// Processed by Angular, for instance called by a ng-click directive
$scope.applyModelSynchronously = function() {
// No need to digest
editModel();
}
// Any kind of asynchronous code, for instance a server request
callServer(function() {
/* That code is not watched nor digested by Angular, thus we
can safely $apply it */
$scope.$apply(editModel);
});
And if you know what you're doing and working on an isolated small directive while part of a big Angular application, you could prefer $digest instead over $apply to save performances.
A new, powerful method has been added to any $scope: $evalAsync. Basically, it will execute its callback within the current digest cycle if one is occurring, otherwise a new digest cycle will start executing the callback.
That is still not as good as a $scope.$digest if you really know that you only need to synchronize an isolated part of your HTML (since a new $apply will be triggered if none is in progress), but this is the best solution when you are executing a function which you cannot know it if will be executed synchronously or not, for instance after fetching a resource potentially cached: sometimes this will require an async call to a server, otherwise the resource will be locally fetched synchronously.
In these cases and all the others where you had a !$scope.$$phase, be sure to use $scope.$evalAsync( callback )
$timeout is critiqued in passing. Can you give more reasons to avoid $timeout ? –
Straightaway $scope.applyAsync() - no one has mentioned this one in any of the answers to this OP but I have seen it in other threads. When I changed all my $scope.apply() to scope.applyAsync() all my $digest cycle errors went away...don't know if I made more problems for myself, but so far no issues. –
Lowenstern Handy little helper method to keep this process DRY:
function safeApply(scope, fn) {
(scope.$$phase || scope.$root.$$phase) ? fn() : scope.$apply(fn);
}
scope.$apply(fn); should be scope.$apply(fn()); because fn() will execute the function and not fn. Please help me to where I am wrong –
Habit I had the same problem with third parties scripts like CodeMirror for example and Krpano, and even using safeApply methods mentioned here haven't solved the error for me.
But what do has solved it is using $timeout service (don't forget to inject it first).
Thus, something like:
$timeout(function() {
// run my code safely here
})
and if inside your code you are using
this
perhaps because it's inside a factory directive's controller or just need some kind of binding, then you would do something like:
.factory('myClass', [
'$timeout',
function($timeout) {
var myClass = function() {};
myClass.prototype.surprise = function() {
// Do something suprising! :D
};
myClass.prototype.beAmazing = function() {
// Here 'this' referes to the current instance of myClass
$timeout(angular.bind(this, function() {
// Run my code safely here and this is not undefined but
// the same as outside of this anonymous function
this.surprise();
}));
}
return new myClass();
}]
)
See http://docs.angularjs.org/error/$rootScope:inprog
The problem arises when you have a call to $apply that is sometimes run asynchronously outside of Angular code (when $apply should be used) and sometimes synchronously inside Angular code (which causes the $digest already in progress error).
This may happen, for example, when you have a library that asynchronously fetches items from a server and caches them. The first time an item is requested, it will be retrieved asynchronously so as not to block code execution. The second time, however, the item is already in cache so it can be retrieved synchronously.
The way to prevent this error is to ensure that the code that calls $apply is run asynchronously. This can be done by running your code inside a call to $timeout with the delay set to 0 (which is the default). However, calling your code inside $timeout removes the necessity to call $apply, because $timeout will trigger another $digest cycle on its own, which will, in turn, do all the necessary updating, etc.
Solution
In short, instead of doing this:
... your controller code...
$http.get('some/url', function(data){
$scope.$apply(function(){
$scope.mydate = data.mydata;
});
});
... more of your controller code...
do this:
... your controller code...
$http.get('some/url', function(data){
$timeout(function(){
$scope.mydate = data.mydata;
});
});
... more of your controller code...
Only call $apply when you know the code running it will always be run outside of Angular code (e.g. your call to $apply will happen inside a callback that is called by code outside of your Angular code).
Unless someone is aware of some impactful disadvantage to using $timeout over $apply, I don't see why you couldn't always use $timeout (with zero delay) instead of $apply, as it will do approximately the same thing.
$apply myself but still getting the error. –
Selfmortification $apply is synchronous (its callback is executed, then the code following $apply) while $timeoutis not: the current code following timeout is executed, then a new stack begins with its callback, as if you were using setTimeout. That could lead to graphic glitches if you were updating twice the same model: $timeout will wait for the view to get refreshed before updating it again. –
Cutshall When you get this error, it basically means that it's already in the process of updating your view. You really shouldn't need to call $apply() within your controller. If your view isn't updating as you would expect, and then you get this error after calling $apply(), it most likely means you're not updating the the model correctly. If you post some specifics, we could figure out the core problem.
you're not updating the the model correctly? $scope.err_message = 'err message'; is not correct update? –
Characteristically $apply() is when you update the model "outside" of angular(e.g. from a jQuery plugin). It's easy to fall into the trap of the view not looking right, and so you throw a bunch of $apply()s everywhere, which then ends up with the error seen in the OP. When I say you're not updating the the model correctly I just mean all the business logic not correctly populating anything that might be in the scope, which leads to the view not looking as expected. –
Butyrin The shortest form of safe $apply is:
$timeout(angular.noop)
You can also use evalAsync. It will run sometime after digest has finished!
scope.evalAsync(function(scope){
//use the scope...
});
First of all, don’t fix it this way
if ( ! $scope.$$phase) {
$scope.$apply();
}
It does not make sense because $phase is just a boolean flag for the $digest cycle, so your $apply() sometimes won’t run. And remember it’s a bad practice.
Instead, use $timeout
$timeout(function(){
// Any code in here will automatically have an $scope.apply() run afterwards
$scope.myvar = newValue;
// And it just works!
});
If you are using underscore or lodash, you can use defer():
_.defer(function(){
$scope.$apply();
});
Sometimes you will still get errors if you use this way (https://mcmap.net/q/53562/-angularjs-prevent-error-digest-already-in-progress-when-calling-scope-apply).
Try this:
if(! $rootScope.$root.$$phase) {
...
$rootScope and anyScope.$root are the same guy. $rootScope.$root is redundant. –
Cutshall You should use $evalAsync or $timeout according to the context.
This is a link with a good explanation:
http://www.bennadel.com/blog/2605-scope-evalasync-vs-timeout-in-angularjs.htm
try using
$scope.applyAsync(function() {
// your code
});
instead of
if(!$scope.$$phase) {
//$digest or $apply
}
$applyAsync Schedule the invocation of $apply to occur at a later time. This can be used to queue up multiple expressions which need to be evaluated in the same digest.
NOTE: Within the $digest, $applyAsync() will only flush if the current scope is the $rootScope. This means that if you call $digest on a child scope, it will not implicitly flush the $applyAsync() queue.
Exmaple:
$scope.$applyAsync(function () {
if (!authService.authenticated) {
return;
}
if (vm.file !== null) {
loadService.setState(SignWizardStates.SIGN);
} else {
loadService.setState(SignWizardStates.UPLOAD_FILE);
}
});
References:
1.Scope.$applyAsync() vs. Scope.$evalAsync() in AngularJS 1.3
I would advise you to use a custom event rather than triggering a digest cycle.
I've come to find that broadcasting custom events and registering listeners for this events is a good solution for triggering an action you wish to occur whether or not you are in a digest cycle.
By creating a custom event you are also being more efficient with your code because you are only triggering listeners subscribed to said event and NOT triggering all watches bound to the scope as you would if you invoked scope.$apply.
$scope.$on('customEventName', function (optionalCustomEventArguments) {
//TODO: Respond to event
});
$scope.$broadcast('customEventName', optionalCustomEventArguments);
yearofmoo did a great job at creating a reusable $safeApply function for us :
Usage :
//use by itself
$scope.$safeApply();
//tell it which scope to update
$scope.$safeApply($scope);
$scope.$safeApply($anotherScope);
//pass in an update function that gets called when the digest is going on...
$scope.$safeApply(function() {
});
//pass in both a scope and a function
$scope.$safeApply($anotherScope,function() {
});
//call it on the rootScope
$rootScope.$safeApply();
$rootScope.$safeApply($rootScope);
$rootScope.$safeApply($scope);
$rootScope.$safeApply($scope, fn);
$rootScope.$safeApply(fn);
I have been able to solve this problem by calling $eval instead of $apply in places where I know that the $digest function will be running.
According to the docs, $apply basically does this:
function $apply(expr) {
try {
return $eval(expr);
} catch (e) {
$exceptionHandler(e);
} finally {
$root.$digest();
}
}
In my case, an ng-click changes a variable within a scope, and a $watch on that variable changes other variables which have to be $applied. This last step causes the error "digest already in progress".
By replacing $apply with $eval inside the watch expression the scope variables get updated as expected.
Therefore, it appears that if digest is going to be running anyways because of some other change within Angular, $eval'ing is all you need to do.
Understanding that the Angular documents call checking the $$phase an anti-pattern, I tried to get $timeout and _.defer to work.
The timeout and deferred methods create a flash of unparsed {{myVar}} content in the dom like a FOUT. For me this was not acceptable. It leaves me without much to be told dogmatically that something is a hack, and not have a suitable alternative.
The only thing that works every time is:
if(scope.$$phase !== '$digest'){ scope.$digest() }.
I don't understand the danger of this method, or why it's described as a hack by people in the comments and the angular team. The command seems precise and easy to read:
"Do the digest unless one is already happening"
In CoffeeScript it's even prettier:
scope.$digest() unless scope.$$phase is '$digest'
What's the issue with this? Is there an alternative that won't create a FOUT? $safeApply looks fine but uses the $$phase inspection method, too.
This is my utils service:
angular.module('myApp', []).service('Utils', function Utils($timeout) {
var Super = this;
this.doWhenReady = function(scope, callback, args) {
if(!scope.$$phase) {
if (args instanceof Array)
callback.apply(scope, Array.prototype.slice.call(args))
else
callback();
}
else {
$timeout(function() {
Super.doWhenReady(scope, callback, args);
}, 250);
}
};
});
and this is an example for it's usage:
angular.module('myApp').controller('MyCtrl', function ($scope, Utils) {
$scope.foo = function() {
// some code here . . .
};
Utils.doWhenReady($scope, $scope.foo);
$scope.fooWithParams = function(p1, p2) {
// some code here . . .
};
Utils.doWhenReady($scope, $scope.fooWithParams, ['value1', 'value2']);
};
I have been using this method and it seems to work perfectly fine. This just waits for the time the cycle has finished and then triggers apply(). Simply call the function apply(<your scope>) from anywhere you want.
function apply(scope) {
if (!scope.$$phase && !scope.$root.$$phase) {
scope.$apply();
console.log("Scope Apply Done !!");
}
else {
console.log("Scheduling Apply after 200ms digest cycle already in progress");
setTimeout(function() {
apply(scope)
}, 200);
}
}
When I disabled debugger , the error is not happening anymore. In my case, it was because of debugger stopping the code execution.
similar to answers above but this has worked faithfully for me... in a service add:
//sometimes you need to refresh scope, use this to prevent conflict
this.applyAsNeeded = function (scope) {
if (!scope.$$phase) {
scope.$apply();
}
};
You can use $timeout to prevent the error.
$timeout(function () {
var scope = angular.element($("#myController")).scope();
scope.myMethod();
scope.$scope();
}, 1);
The issue is basically coming when, we are requesting to angular to run the digest cycle even though its in process which is creating issue to angular to understanding. consequence exception in console.
1. It does not have any sense to call scope.$apply() inside the $timeout function because internally it does the same.
2. The code goes with vanilla JavaScript function because its native not angular angular defined i.e. setTimeout
3. To do that you can make use of
if(!scope.$$phase){
scope.$evalAsync(function(){
});
}
let $timeoutPromise = null;
$timeout.cancel($timeoutPromise);
$timeoutPromise = $timeout(() => {
$scope.$digest();
}, 0, false);
Here is good solution to avoid this error and avoid $apply
you can combine this with debounce(0) if calling based on external event. Above is the 'debounce' we are using, and full example of code
.factory('debounce', [
'$timeout',
function ($timeout) {
return function (func, wait, apply) {
// apply default is true for $timeout
if (apply !== false) {
apply = true;
}
var promise;
return function () {
var cntx = this,
args = arguments;
$timeout.cancel(promise);
promise = $timeout(function () {
return func.apply(cntx, args);
}, wait, apply);
return promise;
};
};
}
])
and the code itself to listen some event and call $digest only on $scope you need
let $timeoutPromise = null;
let $update = debounce(function () {
$timeout.cancel($timeoutPromise);
$timeoutPromise = $timeout(() => {
$scope.$digest();
}, 0, false);
}, 0, false);
let $unwatchModelChanges = $scope.$root.$on('updatePropertiesInspector', function () {
$update();
});
$scope.$on('$destroy', () => {
$timeout.cancel($update);
$timeout.cancel($timeoutPromise);
$unwatchModelChanges();
});
Found this: https://coderwall.com/p/ngisma where Nathan Walker (near bottom of page) suggests a decorator in $rootScope to create func 'safeApply', code:
yourAwesomeModule.config([
'$provide', function($provide) {
return $provide.decorator('$rootScope', [
'$delegate', function($delegate) {
$delegate.safeApply = function(fn) {
var phase = $delegate.$$phase;
if (phase === "$apply" || phase === "$digest") {
if (fn && typeof fn === 'function') {
fn();
}
} else {
$delegate.$apply(fn);
}
};
return $delegate;
}
]);
}
]);
This will be solve your problem:
if(!$scope.$$phase) {
//TODO
}
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$timeout()– Cideng-*). Ensure, if you are calling it from within a function (that is called via timeout/ajax/events), that it's not also being run on load initially. – Improvisatorelement[0].focus();– Apocarp