AngularJS Prevent error digest already in progress when calling scope apply

Question

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

User · Answer

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

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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

User · Answer

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  angular js Anti Patterns        Don t do if    scope   phase   scope  apply    it means your  scope  apply   isn t high enough in the call stack

User · Answer

let  timeoutPromise   null           timeout cancel  timeoutPromise            timeoutPromise    timeout      gt                 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      gt                     scope  digest                   0  false              0  false            let  unwatchModelChanges    scope  root  on  updatePropertiesInspector   function                   update                           scope  on   destroy        gt                 timeout cancel  update                timeout cancel  timeoutPromise                unwatchModelChanges

User · Answer

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

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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

User · Answer

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   Things you should know     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     How to structure your code  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   Update since Angularjs 1 2  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

User · Answer

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

User · Answer

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

User · Answer

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   AngularJs Docs

User · Answer

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

User · Answer

use  scope   phase     scope  apply    instead

User · Answer

yearofmoo did a great job at creating a reusable  safeApply function for us        https   github com yearofmoo AngularJS-Scope SafeApply   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

User · Answer

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

User · Answer

Handy little helper method to keep this process DRY    function safeApply scope  fn         scope   phase    scope  root   phase    fn     scope  apply fn

User · Answer

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

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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

User · Answer

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

User · Answer

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

User · Answer

When I disabled debugger   the error is not happening anymore  In my case  it was because of debugger stopping the code execution

User · Answer

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  lt your scope gt   from anywhere you want   function apply scope      if   scope   phase  amp  amp   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

User · Answer

You can also use evalAsync  It will run sometime after digest has finished   scope evalAsync function scope         use the scope

User · Answer

You can use  timeout to prevent the error   timeout function          var scope   angular element    quot  myController quot    scope        scope myMethod         scope  scope       1

User · Answer

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

User · Answer

Sometimes you will still get errors if you use this way  https   stackoverflow com a 12859093 801426    Try this   if    rootScope  root   phase

User · Answer

The shortest form of safe  apply is    timeout angular noop

User · Answer

This will be solve your problem   if   scope   phase        TODO

User · Answer

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  amp  amp  typeof fn      function                   fn                              else                delegate  apply fn                                  return  delegate

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