In a particular scenario, I need to call the the github api to retrieve a specific user's info. Then issue a second call to retrieve the user's repositories:
search(login: string): void {
this.user = undefined;
// first call
this.githubApi.getUser(login)
.then(user => {
this.user = user;
// second call
this.githubApi.getRepos(user.repos_url)
.then(reposResponse => {
this.repos = reposResponse.repos;
// I don't like to call this.$scope.$apply() !!;
});
});
}
The first call gets executed and the bound elements to this.user gets updated with no problem in the view.
The second call gets executed and the result is returned successfully and this.repos is set correctly. But, the bound elements on the view are not updated.
If I call this.$scope.$apply() in the very last line of the second callback, it makes the view update work but I guess this is not correct approach.
Any solution?
Well, if you are not willing to use $scope.apply();, try updating your getRepos service response code with:
setTimeout(
() => {
this.repos = reposResponse.repos;
}, 0
)
First you need to know , why Angular-Js is not updating the view.
You have used $scope.$apply(), so I'm assuming you already know , how it works and why we use it. Now , to the problem!
Sometimes when you make a callback - nested callback in particular - Angular does not update the view. Sometimes angular thinks that it does not need to update the view because of callbacks. And the watchers do not take action when the value changes of the variable that they are watching.
Then you use $scope.$apply() to run the digest cycle again (assuming you already know the digest cycle if you don't then let me know). And it makes the watchers to update the view.In your case, digest cycle is not running, that is why angular is not updating the view. If your digest cycle was running , angular would have given you error. So, it will tell angular to run digest cycle again because two-way binding is not working properly.
I don't think there is another way. But if there is a way, I would love to know that way. Also its not a bad approach. It was made for these kind of problems.
Related
I'm looking for a pure angularJS way to call a controller method once a particular dom element is rendered. I'm implementing the scenario of a back button tap, so I need to scroll to a particular element once it is rendered. I'm using http://mobileangularui.com/docs/#scrollable.
Update: how my controller looks like:
$scope.item_ready=function(){
return document.getElementById($scope.item_dom_id).length;
};
$scope.$watch('item_ready', function(new_value, old_value, scope){
//run once on page load, and angular.element() is empty as the element is not yet rendered
});
Thanks
One hack that you could do and I emphasize hack here but sometimes it's just what you need is watch the DOM for changes and execute a function when the DOM hasn't changed for 500ms which is accepted as a fair value to say that the DOM has loaded. A code for this would look like the following:
// HACK: run this when the dom hasn't changed for 500ms logic
var broadcast = function () {};
if (document.addEventListener) {
document.addEventListener("DOMSubtreeModified", function (e) {
//If less than 500 milliseconds have passed, the previous broadcast will be cleared.
clearTimeout(broadcast)
broadcast = $window.setTimeout(function () {
//This will only fire after 500 ms have passed with no changes
// run your code here
}, 10)
});
}
Read this post Calling a function when ng-repeat has finished
But don't look at the accepted answer, use the 3rd answer down by #Josep by using a filter to iterate through all your repeat items and call the function once the $last property returns true.
However instead of using $emit, run your function...This way you don't have to rely on $watch. Have used it and works like a charm...
Background:
I am building my offline application which uses AngularJS for UI and PocuhDB for locally storing the data retrieved from the server.
Issue:
The data retrieved from PouchDB is not getting rendered in the UI.
Controller:
$scope.retrieveView = function (sys, code, majorVer, minorVer) {
var promise;
promise = dataService.getDataFromLocalDb().then(
function(dataFromPouchDb){
$scope.data = dataFromPouchDb.data;
});
return promise;
}
And then in the UI code I have the following :
<h1> {{data}}</h1>
I have debugged the code and everything seem to work fine. But the data is not getting displayed in the UI.
If I hard code a value to the data field then its getting rendered in the UI
$scope.data ="TEST";
This question is kind a old but I just came around it.
Issue is that Angularjs is based on so called digest cycles. When your model or view is changed digest cycle is triggered, watch for changes and update model or view respectively. It is so called two way data binding.
This digest cycle is not triggered periodically on some time base but on events instead. Those events are angular directives like ng-click, ajax calls $http or some other angular events like $timeout. You can find more information about digest here.
In general you should use those things when working with angular application to avoid such situations. In some cases its not possible however like in your case when getting data from DB. Digest cycle is not triggered and your view is not updated by angular.
Workaround for this is manually trigger $digest cycle. Way you have described:
if(!$scope.$$phase) {
$scope.$digest();
}
is working but considered as angular anti-patern and is discouraged by angular team, you should use:
$timeout();
instead. For more information see this answer.
I would maybe consider adding $timeout() call to hook for insert, update, delete hooks or events. Maybe pouchDB sync could be helpfull there.
The code you show seemed correct, maybe you can use console.log() to track the progress of the data. I think the problem might not in this layer. Maybe in the area where you wrapped getDataFromLocalDb(), track and find if the data have transfer to here, or where it disappeared.
The code started to work when i added the following :
if(!$scope.$$phase) {
$scope.$digest();
}
But i have no idea what magic does this code do.
It would be a great help if some some could advice.
The complete code that works now is :
$scope.retrieveView = function (sys, code, majorVer, minorVer) {
var promise;
promise = dataService.getDataFromLocalDb().then(
function(dataFromPouchDb){
$scope.data = dataFromPouchDb.data;
if(!$scope.$$phase) {
$scope.$digest();
}
});
return promise;
}
I'm using the ocModal directive + service (https://github.com/ocombe/ocModal). When someone wants to delete a record they click the delete button which pops up, via ocModal, a modal to confirm.
oc-modal-close ng-click="deleteNote(id)"
So far so good. Within the controller deleteNote runs. Console.log shows the argument is the id I passed. I call an API to delete the note from my database and on a success call a function to delete the note from the Angular variable $scope.notes.
$scope.removeNote = function(id){
console.log(id);
console.log($scope.notes);
delete $scope.notes[id];
console.log($scope.notes);
};
The id is correct and the $scope.notes after the delete command shows it was correctly deleted. Yet, there is no corresponding update on my front-end. Following advise I've seen on Stackover I used apply() which led to a 'digest cycle already in progress' error. I then tried to use $timeout but while that got rid of the digest cycle error, it didn't solve the problem of the bind.
Is it relevant that the $scope.notes is used by a ng-repeat that then uses a directive? I've experimented a bit and don't think so, but just in case wanted to mention it.
Where are you calling $scope.removeNote from? Is it from your main controller or in the modal's controller? maybe a directive?
It feels like it is hitting the wrong scope. You can try to move notes to $scope.model.notes and see if it helps, as it will ensure the correct scope is referenced, but it's hard to say unless you try and provide a fiddle with the issue occurring.
I've created this simple fiddle trying to mimic an API call with $timeout and it works -> http://jsfiddle.net/7eqsc/1/
angular.module('myApp',[])
.controller('myCtrl',function($scope,$timeout){
$scope.notes={
a:'AngularJS',
b:'Rocks'
}
$scope.addRandom=function(){
$scope.notes[parseInt(Math.random()*10000).toString(36)]='New Item';
}
$scope.removeNote=function(id){
//emulate API call
$timeout(function(){
delete $scope.notes[id];
},2000);
}
});
In general, I recommend placing things under an object, such as ".model.yourArray", it ensures references are kept correctly and will save you a lot of trouble.
I've been following this tutorial http://draptik.github.io/blog/2013/07/28/restful-crud-with-angularjs/. I implemented a Grails backend with it instead of the Java one in the tutorial.
I've got the data coming back and forth, with one issue. If I create/update/delete a user, I don't see the changes reflected on my user list when I am redirected back. I have to refresh the page to see the updates.
Looking at the network traffic for an edit, it looks like it does a PUT and fires off the GET before the PUT is complete. Assuming this is because $resource returns a promise so things can be done asynchronously. So how do I handle this so that when $location redirects me, my list is up to date?
I'm guessing the options are to wait for the PUT to complete before redirecting/querying for the list, or to somehow manually manage the $scope.users to match the request?
Or maybe this tutorial is just a bad example? Maybe there is a better way to do it (still using $resource)?
Note: I've seen Restangular out there, and I've seen $http with success callbacks, but I would like to understand the situation above.
One way to overcome this issue would be to not redirect to the list page, till you get a callback, and then do a redirect. You can show some busy indicator till that time. The resource call looks like this.
resource.update(config,data,function() { //gets called on success},
function(error) { //gets called on failure});
In real life scenario waiting for the response of update makes sense as you want to handle the error and success scenarios on the same page.
I don't see your code anywhere so i'm just assuming (based on what you wrote and your current problem)
You are probably doing a full (or partial) get each time you changed a user and (re)binding the result to your scope. Doing this in the callback of the resource should actually start the digest cycle angular does to update modified objects. If you had been doing the fetching outside $resource - for example with custom/jquery ajax you would need to execute $scope.$apply()
What i really don't understand you would need to wait for the callback. You already know you added/modified a user. Instead of 'detaching' that user from your scope, modify it, post it to your rest server, then wait for callback, and reinserting it into the scope - why not modify it directly in the list/array you put on your scope?
var users = Users.get(function () {
$scope.users = users.record; // bind the resulting records to the scope
});
$scope.updateUser = function (user) {
resource.update(...); //pseudo
};
Then in your html, you will keep a reference to the currentUser and the div-list will update automaticly.
<div ng-repeat="user in users" ng-click="currentUser=user">{{user.Name}}</div>
<input ng-model="currentUser.Name">
<button ng-click="updateUser(currentUser);">Update</button>
If you don't want to see the update in the list while you type, but only once your callback fires or when you hit the button, would would instead use another ng-model for your input like this:
<input ng-model="tempUser.Name">
And you would then copy the value other in either the updateUser method or in the resource callback like this:
$scope.updateUser = function (user) {
user.Name = $scope.tempUser.Name; // should update automaticly
resource.update(...) // pseudo
}
Hope it helped!
I'm pretty new to Angular and I'm using firebase as my backend. I was hoping someone could debug this issue. When I first go to my page www.mywebsite.com/#defaultHash the data doesn't load into the DOM, it does after visiting another hash link and coming back though.
My controller is like this:
/* initialize data */
var fb = new Firebase('https://asdf.firebaseio.com/');
/* set data to automatically update on change */
fb.on('value', function(snapshot) {
var data = snapshot.val();
$scope.propertyConfiguration = data.products;
console.log($scope.propertyConfiguration);
console.log("Data retrieved");
});
/* save data on button submit */
$scope.saveConfigs = function(){
var setFBref = new Firebase('https://asdf.firebaseio.com/products');
setFBref.update($scope.propertyConfiguration);
console.log("configurations saved!");
};
I have 3 hash routes say "Shared", "Registration", and "Home" with otherwise.redirectTo set to "Shared".(They all use this controller) Here's the error that occurs: (all "links" are href="#hashWhereever")
1) Go to website.com/#Shared or just refresh. Console logs $scope.propertyConfiguration and "Data Retrieved". DOM shows nothing.
2) Click to website.com/#Registration, console logs $scope data properly, DOM is loaded correctly.
3) Click back to website.com/#Shared, console logs $scope data properly yet this time DOM loads correctly.
4) Refresh currently correctly loaded website.com/#Shared. DOM elements disappear.
Since $scope.data is correct in all the cases here, shouldn't Angular make sure the DOM reflects the model properly? Why is it that the DOM loads correctly only when I am clicking to the page from another link.
I can "fix" it by adding window.location.hash = "Shared" but it throws a huge amount of errors in the console.
FIXED:(sorta)
The function $scope.$apply() forces the view to sync with the model. I'd answer this question myself and close it but I'm still wondering why the view doesn't load correctly when I correctly assign a value to $scope. If Angular's "dirty checking" checks whenever there is a possibility the model has changed, doesn't assigning a value to $scope overqualify?
Angular has no way to know you've assigned a value to $scope.variable. There's no magic here. When you run a directive (ng-click/ng-submit) or Angular internal functions, they all call $apply() and trigger a digest (a check of the dirty flags and update routine).
A possibly safer approach than $apply would be to use $timeout. Currently, if you call a write op in Firebase, it could synchronously trigger an event listener (child_added, child_changed, value, etc). This could cause you to call $apply while still within a $apply scope. If you do this, an Error is thrown. $timeout bypasses this.
See this SO Question for a bit more on the topic of digest and $timeout.
This doc in the Angular Developer Guide covers how compile works; very great background read for any serious Angular dev.
Also, you can save yourself a good deal of energy by using the official Firebase bindings for Angular, which already take all of these implementation details into account.
Vaguely Related Note: In the not-too-distant future, Angular will be able to take advantage of Object.observe magic to handle these updates.