I've discovered that when I use ng-include it gets called far too often.
Every time you click one of the Nothing buttons or change Views, or type something in the input box, getView gets run several times. Up to 6 times when changing views. Basically doing anything that alters the $scope will generate a call to getView.
I've created a plunker to show the behavior I'm describing: plnkr.co
Is this normal behavior and is there any way to make it only run once? I'm worried I may be losing performance due to this.
MY CODE:
index.html
<body ng-app="includeExample">
<div ng-controller="ExampleController">
<div class="row">
<input type="text" ng-model="unrelated">
</div>
<div class="row">
<tabset>
<tab heading="View 1">
<ng-include src="getView('template1')"></ng-include>
</tab>
<tab heading="View 2">
<ng-include src="getView('template2')"></ng-include>
</tab>
</tabset>
</div>
</div>
</body>
Script.js
angular.module('includeExample', ['ngAnimate', 'ui.bootstrap'])
.controller('ExampleController', ['$scope',
function($scope) {
$scope.getView = function(filename) {
console.log("getView " + new Date());
return filename + ".html";
};
}
]);
Template1.html
Content of template1.html
<button type="button" class="btn btn-primary" ng-click="">Nothing</button>
Angular is calling your getView method each time a digest runs to make sure the value hasn't changed. This is part of the "magic" for how angular binds the model and the view together. If you look at the network tab for your development tools you will see that the template is not actually being retrieved by the browser each time the digest runs. Knowing that this is how the digest actually works - you should develop code accordingly running intensive operations in methods that are not directly bound to the view!
For more information on the digest itself see:
http://angular-tips.com/blog/2013/08/watch-how-the-apply-runs-a-digest/
https://docs.angularjs.org/guide/scope (search for "Scope Life Cycle")
https://www.ng-book.com/p/The-Digest-Loop-and-apply/
Hope that helps!
Yeah, angularJS will go through getView() every time you do anything. A good first iteration would be to assign it to a json object instead of using a get method. Actually, it's better if you don't use any get type methods in the html. Then if you really want it to not change, you can remove the 2 way binding (Render value without data-binding).
Related
I have a simple controller
angular.module('datahubApp')
.controller('LoginController',[ '$scope' , '$resource', LoginController]);
function LoginController($scope,$resource){
console.log('Constructor called');
}
I have used the this in HTML in 2 places for two different components, in the same view
<div ng-controller="Logincontroller as ln"> </div>
<div ng-controller="Logincontroller as ln"> </div>
Now when I run the app, i see this in console
Constructor Called
Constructor Called
Constructor Called
Question 1:
So, this is getting called thrice. Is this normal.
Question 2:
In that case, how can I pass the scope variable between components?
Why are you using same controller two times in a view. Use it one time only and it would work perfect.
You can use like:
<div ng-controller="Logincontroller as ln">
<div></div> <!-- Your first div -->
<div> </div> <!-- Your second div -->
</div>
AngularJS will call a controller every time it found in a view. No matter how much time is there in view part.
I have two controllers allocated to two views:
[ResultsView ng-controller="ResultsCtrl"]
[SearchView ng-controller="SearchCtrl"]
The Search View has many complex filters/options and is filled in by the user, then he/she can press "Search" on SearchView and Results should be populated into a Grid.
Now I can send information between two either by a Service or by using $rootScope.$broadcast.
Heres the problem I've run into:
[ResultsView ng-controller="ResultsCtrl"][SearchView ng-controller="SearchCtrl"]
[ResultsView ng-controller="ResultsCtrl"][SearchView ng-controller="SearchCtrl"]
[ResultsView ng-controller="ResultsCtrl"][SearchView ng-controller="SearchCtrl"]
If I were to have multiple Result-Search sections on the same page, how can I ensure they each act independently from each other? Using the Service approach, the ResultsCtrl and SearchCtrl both have the defined service
.controller("searchCtrl", ["$scope", "$searchHttp", function ($scope, $searchHttp) {
.controller("resultsCtrl", ["$scope", "$searchHttp", function ($scope, $searchHttp) {
So I can't change how each instance of the controller behaves regarding the service. Soon as one SearchCtrl calls the service, it will modify every ResultsCtrl instance.
Likewise using broadcasts $rootScope.$broadcast("searchResults"... will be picked up by every ResultsCtrl instance.
So whats the best way around this? I want to reuse the Results and Search View code since its basically the same. But I need to render each pair independently on the same page a few times.
I think the HTML structure you need is something like this.
<!--First-->
<div ng-controller="SearchCtrl">
<div ng-controller="ResultsCtrl">
</div>
</div>
<!--Second-->
<div ng-controller="SearchCtrl">
<div ng-controller="ResultsCtrl">
</div>
</div>
This HTML structure would help you to use independently the search results one's parent SearchCtrl created in ResultsCtrl.
jsfiddle is here.
I hope this would help you. :)
Suppose that I've written a web page that requires the user to key in data into forms. Suppose that there are two parts of the page that are completely separate in the DOM, yet are logically related. I need to bind them to a single model.
The first (bad) solution I can think of is to completely restructure the page so that everything to be bound to the model is contained in a single <div> element (or perhaps even put the controller on the <body> element).
Another solution might be to bind the inputs to a object that could be made a member of two different controllers, but that sounds like a bit of a kludge.
Suppose the HTML looks like this:
<input ng-model='data1' />
<div>
<!-- something complicated -->
</div>
<input ng-model='data2' />
You can create a shared service and inject into both controllers. This can be achieved by either the factory or service pattern. See SO post angular.service vs angular.factory for some insight on the difference/similarity between the two.
This is the Angular way to do this. See the AngularJS services docs for more information. A simple example may include...
<div ng-app="app">
<div ng-controller="ctrlA"></div>
<div ng-controller="ctrlB"></div>
</div>
app.service('sharedService', [function () {
this.someValue = 'yo!'
}]);
app.controller('ctrlB', ['$scope', 'sharedService', function($scope, sharedService) {
console.log(sharedService.someValue) // yo!
}]);
app.controller('ctrlA', ['$scope', 'sharedService', function($scope, sharedService) {
console.log(sharedService.someValue) // yo!
}]);
JSFiddle Link
I'm quite new to angular and frontend in general, but what i'd like to see is something similar to what routing with ngView gives, but without routing, i.e just load a template on some event. To be more specific, let's say i have an input field somewhere in the header and when i click/focus on this field a special panel with different input options shows up. The trick is that this input field and other elements are already a part of a template which is loaded into ngView, so as i understand i can't use another ngView for options pane.
use ngIf, ngShow, ngHide, ngSwitch for stuff like that
<button ng-click="showStuff = true">Show Stuff</button>
<button ng-click="showStuff = false">Hide Stuff</button>
<div ng-show="showStuff">Showing Stuff</div>
<div ng-hide="showStuff">Hiding Stuff</div>
Have a look at this plunker for a quick and dirty, working example.
Note that the showStuff variable is just magically created by angular on the root scope, since I'm not using a controller.
You can load templates with ng-if and ng-include like this example:
<body ng-app="app">
<div class='container'>
<button ng-click='tmpl = true' class='btn btn-info'>Load template!</button>
<div ng-if='tmpl'>
<div ng-include="'template.html'"></div>
</div>
</div>
</body>
The ngIf directive will add element to the DOM when the argument expression is true. Then, the angular will compile the inner directive ngInclude, loading the template.
So, I can change a model value from a child controller, but when the child controller is in ng-switch then it doesn't work, why? I created an example to demonstrate it.
One way to avoid this is to use the . in the model name, like bunnies.kills. Is this a bug or this is a feature ?
Using Angular 1.0.6
Using your code structure, in your child controllers you would need to change:
$scope.$parent.kills++;
to
$scope.$parent.$parent.kills++;
Explanation: MainCtrl's scope is the parent scope of SimpleParentCtrl, but the grandparent of Step1Ctrl and Step2Ctrl. As some others pointed out, ng-switch creates its own scope, and then your Step1Ctrl and Step2Ctrl each created a child scope of the ng-switch.
Note: Each time the 1 or 2 button is clicked, both the ng-switch and it's currently matched child controller get a new scope.
Also: In case you happen to be looking in the Angular source and wondering how the ng-switch directive creates its own scope without a scope property, the answer is that it does so manually in its link method via scope.$new(). The directives ng-include, ng-switch, ng-repeat, and ng-view all create new scope this way, either in the link method or the compile method's returned link function.
Resources:
https://github.com/angular/angular.js/wiki/The-Nuances-of-Scope-Prototypal-Inheritance
http://www.youtube.com/watch?v=ZhfUv0spHCY&feature=youtu.be&t=30m
ng-switch creates its own child scope, which is why #sh0ber's answer is one way to get it to work. In general, models should be referenced in controller scopes (hence reference objects), and not be not primitives. So using a . is a "best practice".
This is not a bug, but it is not a feature either. This is the way JavaScript prototypal inheritance works with primitives.
I would take a slightly different approach to this problem.
Rather than use $scope.$parent, I would recommend you move all of your bunny killing logic into a shared service/model.
Also, I would try to avoid referencing parent views/controllers. Referencing the parent can make it difficult to reuse your code and can be painful to debug as the project grows. It is okay for a parent to know about it's children but a child should know little to nothing about it's parent.
Here is an updated Plunk: http://plnkr.co/edit/PLDbfU8Fu7m59A42qdR6?p=preview
HTML
<body ng-controller="MainCtrl">
<p>
Dead bunnies: <strong>{{Elmer.deadWabbits}}</strong>
</p>
<div ng-controller="SimpleParentCtrl">
<button ng-click="Elmer.killTheWabbit()">Kill from simple parent gun</button>
</div>
<hr>
<div ng-switch="" on="step">
<div ng-switch-when="first" ng-controller="Step1Ctrl">
<button ng-click="Elmer.killTheWabbit()">Kill from 1 tab gun</button>
</div>
<div ng-switch-when="second">
<div ng-controller="Step2Ctrl">
<button ng-click="Elmer.killTheWabbit()">Kill from 2 tab gun</button>
</div>
</div>
</div>
<hr>
<p>
<button ng-click="changeStep('first')">1</button> <button ng-click="changeStep('second')">2</button>
</p>
</body>
JS
angular.module('plunker', []).
service("Elmer", [function() {
this.deadWabbits = 0;
this.killTheWabbit = function() {
this.deadWabbits++;
};
}]).
controller('MainCtrl', function($scope, Elmer) {
$scope.Elmer = Elmer;
$scope.step = 'first';
$scope.changeStep = function(name){
$scope.step = name;
};
}).
controller('SimpleParentCtrl', function() {}).
controller('Step1Ctrl', function() {}).
controller('Step2Ctrl', function() {});
One way to avoid this is to use the . in model name, like bunnies.kills. Is this a bug or this is a feature ?
This has been explained numberous times : https://github.com/angular/angular.js/wiki/The-Nuances-of-Scope-Prototypal-Inheritance
and in mhevery's video