While transitioning an existing angular site, I encountered an annoying problem. The initial symptom was that a certain controller was not running it's initialize function immediately following the login. I logged and I tracked, and eventually I realized it was a design flaw of the page. Essentially, index.html contains a <header>, <ng-view>, and <footer>. There are a couple of ng-if attributes that live in the header that I want to evaluate after the login, but since the view is the only thing that is reloaded, it was not reinitializing the header controller, and thus not updating the ng-if values.
Then I was reminded of ngInclude, which seems like the perfect solution, until I got it hooked up and realize that doesn't work either. It loads the template the first time, and doesn't reinitialize when the view changes. So then I got the bright idea of passing the HeaderController to another controller or service, and controlling this one stubborn boolean value through a proxy of sorts. That also didn't work. Then I tried putting a function and a boolean into another service, and mirroring that property in the header controller, but thus far I have not gotten this working.
I have done plenty of research about multiple views in the index, and so far I hear a lot about this ui-router, but I'm still not convinced that is the way I want to go. It does not seem to be a simple solution. I have not tried putting the ng-include into the templates yet either, because then I feel like that is going back in time to when we had to update 100 pages every time we changed the menu.
I lost a whole day to this. If anyone could tell me how to trigger the evaluation of this one property in my header controller which I would like to live outside the other templates, please let me know!
Ok so you need to know in your HeaderController when the view has reloaded. There's a number of ways of doing this but the easier and maybe the more correct in this particular case is with an event.
So when you are refreshing the view you just do this, let's say you need the new value of ob1 and ob2 variables.
// ViewController
$rootScope.$emit('viewRefresh', {ob1: 'newvalue1', ob2: 'newvalue2'});
And in your HeaderController you need to listen for that event, and set on your $scope the new values for those attrs (if you're not using controller as syntax).
// HeaderController
$rootScope.$on('viewRefresh', function onRefresh(event, data) {
$scope.ob1 = data.ob1;
$scope.ob2 = data.ob2;
})
Another Solution
Sharing a Promise through a Service (using $q)
function HeaderService($q) {
var defer = $q.defer();
return {
getPromise: function() {return defer.promise},
notify: function(data) {defer.notify(data)}
}
}
function HeaderController(HeaderService) {
var vm = this;
HeaderService.getPromise().then(function(data) {
vm.ob1 = data.ob1;
vm.ob2 = data.ob2;
})
}
function ViewController(HeaderService) {
var data = {ob1: 'newvalue1', ob2: 'newvalue2'};
HeaderService.notify(data)
}
I have a page and a model on my scope $scope.model = { ... };
I bind values on my page with values on the model which is nice. I have an address nested somewhere in that model, for the sake of this example lets say
$scope.model = { visits : [{date : ..., addresses : [{ ... }, ...]},
...], ...};
I need to write all the information of the first visits first address somewhere in a div. I know i can type all the fields like this model.visits[0].addresses[0].Zip etc. but there are like 5 fields in model.visits[0].addresses[0] that i need to output. I figured, there most be an easier way? I considered putting a
<div ng-init="a = model.visits[0].addresses[0]">{{a.Zip}}...</div>
and then just access all properties like that. What i really want though, it not to create a new property on the scope called a unless i can narrow the scope for a to just that one div.
Is that possible somehow?
Clarification: I know i can probably redo my model or move the data up on model itself, but this is just something I've run into multiple times and i would just really want to know if there is a solution to a problem like this.
You could create a tiny directive that creates a new scope on the elements you want:
...
angular.module('yourApp').directive('newScope', function () {
return {scope: true};
});
Then you can use it like this:
<div ng-init="tmp=model.visits[0].addresses[0]" new-scope>{{tmp.Zip}}...</div>
Now, the tmp property will be attached to the new scope created by the newScope directive and will not affect the parent scope.
See, also, this short demo.
I have an array of items bound to <li> elements in a <ul> with AngularJS. I want to be able to click "remove item" next to each of them and have the item removed.
This answer on StackOverflow allows us to do exactly that, but because the name of the array which the elements are being deleted from is hardcoded it is not usable across lists.
You can see an example here on JSfiddle set up, if you try clicking "remove" next to a Game, then the student is removed, not the game.
Passing this back from the button gives me access to the Angular $scope at that point, but I don't know how to cleanly remove that item from the parent array.
I could have the button defined with ng-click="remove('games',this)" and have the function look like this:
$scope.remove = function (arrayName, scope) {
scope.$parent[arrayName].splice(scope.$index,1);
}
(Like this JSFiddle) but naming the parent array while I'm inside it seems like a very good way to break functionality when I edit my code in a year.
Any ideas?
I did not get why you were trying to pass this .. You almost never need to deal with this in angular. ( And I think that is one of its strengths! ).
Here is a fiddle that solves the problem in a slightly different way.
http://jsfiddle.net/WJ226/5/
The controller is now simplified to
function VariousThingsCtrl($scope) {
$scope.students = students;
$scope.games = games;
$scope.remove = function (arrayName,$index) {
$scope[arrayName].splice($index,1);
}
}
Instead of passing the whole scope, why not just pass the $index ? Since you are already in the scope where the arrays are located, it should be pretty easy from then.
I’m looking for the best practice of how to bind to a service property in AngularJS.
I have worked through multiple examples to understand how to bind to properties in a service that is created using AngularJS.
Below I have two examples of how to bind to properties in a service; they both work. The first example uses basic bindings and the second example used $scope.$watch to bind to the service properties
Are either of these example preferred when binding to properties in a service or is there another option that I’m not aware of that would be recommended?
The premise of these examples is that the service should updated its properties “lastUpdated” and “calls” every 5 seconds. Once the service properties are updated the view should reflect these changes. Both these example work successfully; I wonder if there is a better way of doing it.
Basic Binding
The following code can be view and ran here: http://plnkr.co/edit/d3c16z
<html>
<body ng-app="ServiceNotification" >
<div ng-controller="TimerCtrl1" style="border-style:dotted">
TimerCtrl1 <br/>
Last Updated: {{timerData.lastUpdated}}<br/>
Last Updated: {{timerData.calls}}<br/>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.js"></script>
<script type="text/javascript">
var app = angular.module("ServiceNotification", []);
function TimerCtrl1($scope, Timer) {
$scope.timerData = Timer.data;
};
app.factory("Timer", function ($timeout) {
var data = { lastUpdated: new Date(), calls: 0 };
var updateTimer = function () {
data.lastUpdated = new Date();
data.calls += 1;
console.log("updateTimer: " + data.lastUpdated);
$timeout(updateTimer, 5000);
};
updateTimer();
return {
data: data
};
});
</script>
</body>
</html>
The other way I solved binding to service properties is to use $scope.$watch in the controller.
$scope.$watch
The following code can be view and ran here: http://plnkr.co/edit/dSBlC9
<html>
<body ng-app="ServiceNotification">
<div style="border-style:dotted" ng-controller="TimerCtrl1">
TimerCtrl1<br/>
Last Updated: {{lastUpdated}}<br/>
Last Updated: {{calls}}<br/>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.js"></script>
<script type="text/javascript">
var app = angular.module("ServiceNotification", []);
function TimerCtrl1($scope, Timer) {
$scope.$watch(function () { return Timer.data.lastUpdated; },
function (value) {
console.log("In $watch - lastUpdated:" + value);
$scope.lastUpdated = value;
}
);
$scope.$watch(function () { return Timer.data.calls; },
function (value) {
console.log("In $watch - calls:" + value);
$scope.calls = value;
}
);
};
app.factory("Timer", function ($timeout) {
var data = { lastUpdated: new Date(), calls: 0 };
var updateTimer = function () {
data.lastUpdated = new Date();
data.calls += 1;
console.log("updateTimer: " + data.lastUpdated);
$timeout(updateTimer, 5000);
};
updateTimer();
return {
data: data
};
});
</script>
</body>
</html>
I’m aware that I can use $rootscope.$broadcast in the service and $root.$on in the controller, but in other examples that I’ve created that use $broadcast/$on the first broadcast is not captured by the controller, but additional calls that are broadcasted are triggered in the controller. If you are aware of a way to solve $rootscope.$broadcast problem, please provide an answer.
But to restate what I mentioned earlier, I would like to know the best practice of how to bind to a service properties.
Update
This question was originally asked and answered in April 2013. In May 2014, Gil Birman provided a new answer, which I changed as the correct answer. Since Gil Birman answer has very few up-votes, my concern is that people reading this question will disregard his answer in favor of other answers with many more votes. Before you make a decision on what's the best answer, I highly recommend Gil Birman's answer.
Consider some pros and cons of the second approach:
0 {{lastUpdated}} instead of {{timerData.lastUpdated}}, which could just as easily be {{timer.lastUpdated}}, which I might argue is more readable (but let's not argue... I'm giving this point a neutral rating so you decide for yourself)
+1 It may be convenient that the controller acts as a sort of API for the markup such that if somehow the structure of the data model changes you can (in theory) update the controller's API mappings without touching the html partial.
-1 However, theory isn't always practice and I usually find myself having to modify markup and controller logic when changes are called for, anyway. So the extra effort of writing the API negates it's advantage.
-1 Furthermore, this approach isn't very DRY.
-1 If you want to bind the data to ng-model your code become even less DRY as you have to re-package the $scope.scalar_values in the controller to make a new REST call.
-0.1 There's a tiny performance hit creating extra watcher(s). Also, if data properties are attached to the model that don't need to be watched in a particular controller they will create additional overhead for the deep watchers.
-1 What if multiple controllers need the same data models? That means that you have multiple API's to update with every model change.
$scope.timerData = Timer.data; is starting to sound mighty tempting right about now... Let's dive a little deeper into that last point... What kind of model changes were we talking about? A model on the back-end (server)? Or a model which is created and lives only in the front-end? In either case, what is essentially the data mapping API belongs in the front-end service layer, (an angular factory or service). (Note that your first example--my preference-- doesn't have such an API in the service layer, which is fine because it's simple enough it doesn't need it.)
In conclusion, everything does not have to be decoupled. And as far as decoupling the markup entirely from the data model, the drawbacks outweigh the advantages.
Controllers, in general shouldn't be littered with $scope = injectable.data.scalar's. Rather, they should be sprinkled with $scope = injectable.data's, promise.then(..)'s, and $scope.complexClickAction = function() {..}'s
As an alternative approach to achieve data-decoupling and thus view-encapsulation, the only place that it really makes sense to decouple the view from the model is with a directive. But even there, don't $watch scalar values in the controller or link functions. That won't save time or make the code any more maintainable nor readable. It won't even make testing easier since robust tests in angular usually test the resulting DOM anyway. Rather, in a directive demand your data API in object form, and favor using just the $watchers created by ng-bind.
Example
http://plnkr.co/edit/MVeU1GKRTN4bqA3h9Yio
<body ng-app="ServiceNotification">
<div style="border-style:dotted" ng-controller="TimerCtrl1">
TimerCtrl1<br/>
Bad:<br/>
Last Updated: {{lastUpdated}}<br/>
Last Updated: {{calls}}<br/>
Good:<br/>
Last Updated: {{data.lastUpdated}}<br/>
Last Updated: {{data.calls}}<br/>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.js"></script>
<script type="text/javascript">
var app = angular.module("ServiceNotification", []);
function TimerCtrl1($scope, Timer) {
$scope.data = Timer.data;
$scope.lastUpdated = Timer.data.lastUpdated;
$scope.calls = Timer.data.calls;
};
app.factory("Timer", function ($timeout) {
var data = { lastUpdated: new Date(), calls: 0 };
var updateTimer = function () {
data.lastUpdated = new Date();
data.calls += 1;
console.log("updateTimer: " + data.lastUpdated);
$timeout(updateTimer, 500);
};
updateTimer();
return {
data: data
};
});
</script>
</body>
UPDATE: I've finally come back to this question to add that I don't think that either approach is "wrong". Originally I had written that Josh David Miller's answer was incorrect, but in retrospect his points are completely valid, especially his point about separation of concerns.
Separation of concerns aside (but tangentially related), there's another reason for defensive copying that I failed to consider. This question mostly deals with reading data directly from a service. But what if a developer on your team decides that the controller needs to transform the data in some trivial way before the view displays it? (Whether controllers should transform data at all is another discussion.) If she doesn't make a copy of the object first she might unwittingly cause regressions in another view component which consumes the same data.
What this question really highlights are architectural shortcomings of the typical angular application (and really any JavaScript application): tight coupling of concerns, and object mutability. I have recently become enamored with architecting application with React and immutable data structures. Doing so solves the following two problems wonderfully:
Separation of concerns: A component consumes all of it's data via props and has little-to-no reliance on global singletons (such as Angular services), and knows nothing about what happened above it in the view hierarchy.
Mutability: All props are immutable which eliminates the risk of unwitting data mutation.
Angular 2.0 is now on track to borrow heavily from React to achieve the two points above.
From my perspective, $watch would be the best practice way.
You can actually simplify your example a bit:
function TimerCtrl1($scope, Timer) {
$scope.$watch( function () { return Timer.data; }, function (data) {
$scope.lastUpdated = data.lastUpdated;
$scope.calls = data.calls;
}, true);
}
That's all you need.
Since the properties are updated simultaneously, you only need one watch. Also, since they come from a single, rather small object, I changed it to just watch the Timer.data property. The last parameter passed to $watch tells it to check for deep equality rather than just ensuring that the reference is the same.
To provide a little context, the reason I would prefer this method to placing the service value directly on the scope is to ensure proper separation of concerns. Your view shouldn't need to know anything about your services in order to operate. The job of the controller is to glue everything together; its job is to get the data from your services and process them in whatever way necessary and then to provide your view with whatever specifics it needs. But I don't think its job is to just pass the service right along to the view. Otherwise, what's the controller even doing there? The AngularJS developers followed the same reasoning when they chose not to include any "logic" in the templates (e.g. if statements).
To be fair, there are probably multiple perspectives here and I look forward to other answers.
Late to the party, but for future Googlers - don't use the provided answer.
JavaScript has a mechanism of passing objects by reference, while it only passes a shallow copy for values "numbers, strings etc".
In above example, instead of binding attributes of a service, why don't we expose the service to the scope?
$scope.hello = HelloService;
This simple approach will make angular able to do two-way binding and all the magical things you need. Don't hack your controller with watchers or unneeded markup.
And if you are worried about your view accidentally overwriting your service attributes, use defineProperty to make it readable, enumerable, configurable, or define getters and setters. You can gain lots of control by making your service more solid.
Final tip: if you spend your time working on your controller more than your services then you are doing it wrong :(.
In that particular demo code you supplied I would recommend you do:
function TimerCtrl1($scope, Timer) {
$scope.timer = Timer;
}
///Inside view
{{ timer.time_updated }}
{{ timer.other_property }}
etc...
Edit:
As I mentioned above, you can control the behaviour of your service attributes using defineProperty
Example:
// Lets expose a property named "propertyWithSetter" on our service
// and hook a setter function that automatically saves new value to db !
Object.defineProperty(self, 'propertyWithSetter', {
get: function() { return self.data.variable; },
set: function(newValue) {
self.data.variable = newValue;
// let's update the database too to reflect changes in data-model !
self.updateDatabaseWithNewData(data);
},
enumerable: true,
configurable: true
});
Now in our controller if we do
$scope.hello = HelloService;
$scope.hello.propertyWithSetter = 'NEW VALUE';
our service will change the value of propertyWithSetter and also post the new value to database somehow!
Or we can take any approach we want.
Refer to the MDN documentation for defineProperty.
I think this question has a contextual component.
If you're simply pulling data from a service & radiating that information to it's view, I think binding directly to the service property is just fine. I don't want to write a lot of boilerplate code to simply map service properties to model properties to consume in my view.
Further, performance in angular is based on two things. The first is how many bindings are on a page. The second is how expensive getter functions are. Misko talks about this here
If you need to perform instance specific logic on the service data (as opposed to data massaging applied within the service itself), and the outcome of this impacts the data model exposed to the view, then I would say a $watcher is appropriate, as long as the function isn't terribly expensive. In the case of an expensive function, I would suggest caching the results in a local (to controller) variable, performing your complex operations outside of the $watcher function, and then binding your scope to the result of that.
As a caveat, you shouldn't be hanging any properties directly off your $scope. The $scope variable is NOT your model. It has references to your model.
In my mind, "best practice" for simply radiating information from service down to view:
function TimerCtrl1($scope, Timer) {
$scope.model = {timerData: Timer.data};
};
And then your view would contain {{model.timerData.lastupdated}}.
Building on the examples above I thought I'd throw in a way of transparently binding a controller variable to a service variable.
In the example below changes to the Controller $scope.count variable will automatically be reflected in the Service count variable.
In production we're actually using the this binding to update an id on a service which then asynchronously fetches data and updates its service vars. Further binding that means that controllers automagically get updated when the service updates itself.
The code below can be seen working at http://jsfiddle.net/xuUHS/163/
View:
<div ng-controller="ServiceCtrl">
<p> This is my countService variable : {{count}}</p>
<input type="number" ng-model="count">
<p> This is my updated after click variable : {{countS}}</p>
<button ng-click="clickC()" >Controller ++ </button>
<button ng-click="chkC()" >Check Controller Count</button>
</br>
<button ng-click="clickS()" >Service ++ </button>
<button ng-click="chkS()" >Check Service Count</button>
</div>
Service/Controller:
var app = angular.module('myApp', []);
app.service('testService', function(){
var count = 10;
function incrementCount() {
count++;
return count;
};
function getCount() { return count; }
return {
get count() { return count },
set count(val) {
count = val;
},
getCount: getCount,
incrementCount: incrementCount
}
});
function ServiceCtrl($scope, testService)
{
Object.defineProperty($scope, 'count', {
get: function() { return testService.count; },
set: function(val) { testService.count = val; },
});
$scope.clickC = function () {
$scope.count++;
};
$scope.chkC = function () {
alert($scope.count);
};
$scope.clickS = function () {
++testService.count;
};
$scope.chkS = function () {
alert(testService.count);
};
}
I think it's a better way to bind on the service itself instead of the attributes on it.
Here's why:
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.7/angular.min.js"></script>
<body ng-app="BindToService">
<div ng-controller="BindToServiceCtrl as ctrl">
ArrService.arrOne: <span ng-repeat="v in ArrService.arrOne">{{v}}</span>
<br />
ArrService.arrTwo: <span ng-repeat="v in ArrService.arrTwo">{{v}}</span>
<br />
<br />
<!-- This is empty since $scope.arrOne never changes -->
arrOne: <span ng-repeat="v in arrOne">{{v}}</span>
<br />
<!-- This is not empty since $scope.arrTwo === ArrService.arrTwo -->
<!-- Both of them point the memory space modified by the `push` function below -->
arrTwo: <span ng-repeat="v in arrTwo">{{v}}</span>
</div>
<script type="text/javascript">
var app = angular.module("BindToService", []);
app.controller("BindToServiceCtrl", function ($scope, ArrService) {
$scope.ArrService = ArrService;
$scope.arrOne = ArrService.arrOne;
$scope.arrTwo = ArrService.arrTwo;
});
app.service("ArrService", function ($interval) {
var that = this,
i = 0;
this.arrOne = [];
that.arrTwo = [];
$interval(function () {
// This will change arrOne (the pointer).
// However, $scope.arrOne is still same as the original arrOne.
that.arrOne = that.arrOne.concat([i]);
// This line changes the memory block pointed by arrTwo.
// And arrTwo (the pointer) itself never changes.
that.arrTwo.push(i);
i += 1;
}, 1000);
});
</script>
</body>
You can play it on this plunker.
I would rather keep my watchers a less as possible. My reason is based on my experiences and one might argue it theoretically.
The issue with using watchers is that you can use any property on scope to call any of the methods in any component or service you like.
In a real world project, pretty soon you'll end up with a non-tracable (better said hard to trace) chain of methods being called and values being changed which specially makes the on-boarding process tragic.
To bind any data,which sends service is not a good idea (architecture),but if you need it anymore I suggest you 2 ways to do that
1) you can get the data not inside you service.You can get data inside your controller/directive and you will not have a problem to bind it anywhere
2) you can use angularjs events.Whenever you want,you can send a signal(from $rootScope) and catch it wherever you want.You can even send a data on that eventName.
Maybe this can help you.
If you need more with examples,here is the link
http://www.w3docs.com/snippets/angularjs/bind-value-between-service-and-controller-directive.html
What about
scope = _.extend(scope, ParentScope);
Where ParentScope is an injected service?
The Most Elegant Solutions...
app.service('svc', function(){ this.attr = []; return this; });
app.controller('ctrl', function($scope, svc){
$scope.attr = svc.attr || [];
$scope.$watch('attr', function(neo, old){ /* if necessary */ });
});
app.run(function($rootScope, svc){
$rootScope.svc = svc;
$rootScope.$watch('svc', function(neo, old){ /* change the world */ });
});
Also, I write EDAs (Event-Driven Architectures) so I tend to do something like the following [oversimplified version]:
var Service = function Service($rootScope) {
var $scope = $rootScope.$new(this);
$scope.that = [];
$scope.$watch('that', thatObserver, true);
function thatObserver(what) {
$scope.$broadcast('that:changed', what);
}
};
Then, I put a listener in my controller on the desired channel and just keep my local scope up to date this way.
In conclusion, there's not much of a "Best Practice" -- rather, its mostly preference -- as long as you're keeping things SOLID and employing weak coupling. The reason I would advocate the latter code is because EDAs have the lowest coupling feasible by nature. And if you aren't too concerned about this fact, let us avoid working on the same project together.
Hope this helps...
I read several articles about Backbone.js with sample apps but I can't find an explanation or example on how Backbone knows when a widget in a view is clicked and to which model it is bound.
Is it handled by internal assignment of IDs or something?
For example if you want to delete a div with id="123" could remove it from the DOM with jQuery or javascript functions. In backbone this div could be without the id but could be removed without knowing it, right?
If anybody knows a good article or could improve my understanding on that it would be great.
The way the view "knows" the model to which it's bound is done through the _configure method shown below:
_configure: function(options) {
if (this.options) options = _.extend({}, this.options, options);
for (var i = 0, l = viewOptions.length; i < l; i++) {
var attr = viewOptions[i];
if (options[attr]) this[attr] = options[attr];
}
this.options = options;
}
The import block to note is:
for (var i = 0, l = viewOptions.length; i < l; i++) {
var attr = viewOptions[i];
if (options[attr]) this[attr] = options[attr];
}
viewOptions is an array of keys that have "special" meaning to a view. Here's the array:
var viewOptions = ['model', 'collection', 'el', 'id', 'attributes', 'className', 'tagName'];
This loop is the "glue" between view and model or view and collection. If they're present in the options, they're assigned automatically.
All this is in the annotated source code.
Check http://www.joezimjs.com/javascript/introduction-to-backbone-js-part-1-models-video-tutorial/.
Even if it looks complicated, there's so little to learn, trust me.
If you ask more specifically I could try to help.
Reading the source is probably your best bet for improving your understanding. The Backbone function you want to look at is called delegateEvents. But the short version is that it uses the jQuery delegate() function. The root element is the View's element (the el property), and it's filtered by whatever selector you provided.
jQuery doesn't actually bind a handler to each element that you're listening to. Instead it lets the events bubble up to the root element and inspects them there. Since there's nothing attached to each individual element you can delete them freely without causing any problems. However some methods of deleting the View's element (eg, by setting innerHTML on a parent element) might cause a memory leak. I'm not 100% sure about that, but it's probably best to just not do that anyway.