Angular.js $scope.$on initial value - javascript

I'm using angular.js $scope.$on for listening for events from my service(event got triggered on service data change).
I use the following code snippet:
$scope.people = contacts.people;
$scope.$on('contacts-changed', () => {
$scope.people = contacts.people;
});
Is there any way to extend angular to avoid the first line and trigger $scope.$on('contacts-changed') or similar by default on the time of event bind?
I was looking in angular.js decorators but not sure how can I decorate $scope to add $scope.$bind or similar method
Ideas?

Sometimes the solution is so simple, but you need to think outside of the box. Move the event callback block into a function and just run it when the controller loads, after the event binding.
See this:
function handlePeople() {
$scope.people = contacts.people;
}
$scope.$on('contacts-changed', handlePeople);
handlePeople();
You can also keep the original code and do a trigger manually.

Temporally went with the following solution:
$rootScope.$bind = (bindName, bindHandler) => {
$rootScope.$on(bindName, bindHandler);
bindHandler();
};
But I'd want to replace it so I could use $scope instead of $rootScope and without defining this in each $scope...
I could try to use $scope._ proto _ but it seems _ proto _ is deprecated

Related

Integrating non-Angular code?

I'm developing a Cordova/PhoneGap app, and I'm using the $cordovaPush plugin (wrapped for PushPlugin) to handle push notifications.
The code looks something like this:
var androidConfig = {
"senderID" : "mysenderID",
"ecb" : "onNotification"
}
$cordovaPush.register(androidConfig).then(function(result) {
console.log('Cordova Push Reg Success');
console.log(result);
}, function(error) {
console.log('Cordova push reg error');
console.log(error);
});
The "ecb" function must be defined with window scope, ie:
window.onNotification = function onNotification(e)...
This function handles incoming events. I'd obviously like to handle incoming events in my angular code - how can I integrate the two so that my onNotification function can access my scope/rootScope variables?
Usually, you'll wrap your 3rd party library in a service or a factory, but in the spirit of answering your particular scenario...
Here's one possibility:
angular.module('myApp').
controller('myController', function($scope, $window) {
$window.onNotification = function() {
$scope.apply(function() {
$scope.myVar = ...updates...
});
};
});
A couple of things to notice:
Try to use $window, not window. It's a good habit to get into as it will help you with testability down the line. Because of the internals of Cordova, you might actually need to use window, but I doubt it.
The function that does all of the work is buried inside of $scope.apply. If you forget to do this, then any variables you update will not be reflected in the view until the digest cycle runs again (if ever).
Although I put my example in a controller, you might put yours inside of a handler. If its an angular handler (ng-click, for example), you might think that because the ng-click has an implicit $apply wrapping the callback, your onNotification function is not called at that time, so you still need to do the $apply, as above.
...seriously... don't forget the apply. :-) When I'm debugging people's code, it's the number one reason why external libraries are not working. We all get bit at least once by this.
Define a kind of a mail controller in body and inside that controller use the $window service.
HTML:
<body ng-controller="MainController">
<!-- other markup .-->
</body>
JS:
yourApp.controller("BaseController", ["$scope", "$window", function($scope, $window) {
$window.onNotification = function(e) {
// Use $scope or any Angular stuff
}
}]);

controller and link functions in directive do not have same scope

I have an issue with my angular.js directive.
It should be a kind of autocomplete, in directive's controller property I'm loading an array of values and inside link function compiling template to show the results.
But when I update scope inside link it doesn't reflect on controller and template, please take look at the example here - http://plnkr.co/edit/Lz3QGwklghPo3as2QTqU
Should I apply scope changes or smth similar?
Your code has two problems
Attach click event to document instead of body
Use $apply() inside bind
Below code will resolve your problem
$document.bind('click', function (e) {
scope.results = [];
scope.$apply();
});
I update your $body.bind('click',...) method to
$body.bind('change', function (e) {
scope.results = [];
});
and it seemed to work (I mean that after 0.5 sec I typed a letter, the list of name is re-displayed).

update service from directive that uses it

It is possible for a directive to update a service and then use the updated version?
In my service (cfg), I have a variable and an update function...
var test = "unfired";
function updateTest(){
console.log("LOG:","updateTest is firing");
test = "fired";
}
In the linking function of my directive I have
scope.$watch(watcher, function(newVal, oldVal) {
console.log("Before:",cfg.test);
cfg.updateTest();
console.log("After:",cfg.test);
}); //scope.$watch
Even though the updateTest function is firing, the console logs the same value before and after.
Now if cfg were a controller instead of a service I would do something like
function updateTest(){
console.log("LOG:","updateTest is firing");
test = "fired";
cfg.$apply() //or cfg.$digest()
}
But obviously that won't work. I have also tried injecting cfg to the controller and and $apply() to the link function...
console.log("Before:",cfg.test);
scope.$apply(function(){
cfg.updateTest()
});
console.log("After:",cfg.test);
which did trigger updateTest(), but it did not update the cfg service as the directive understands it.
Perhaps another way to say it is that I would like to "reinject" the service into the directive.
If you are wondering why I'd like to do this, it's because I have a bunch of d3.js animations as directives that share the same scales, and I'd like certain events to trigger changes in the scales' domains from one directive to the others.
Rather than using a service to communicate between directives. Try using "broadcast". You can throw an event into the air and anybody listening will run whatever function you want. It works like this.
Directive 1:
$rootScope.$broadcast('event:updateTest');
Directive 2:
$rootScope.$on("event:updateTest", function (event, next, current) { ... }
Then you can deal with local instances of your 'test' variable, rather than a service 'global' variable.

AngularJS controller and methods

I'm a beginner in angularjs with a few questions about controllers.
Here's my example controller:
function exampleController($scope)
{
$scope.sampleArray = new Array();
$scope.firstMethod = function()
{
//initialize the sampleArray
};
$scope.secondMethod = function()
{
this.firstMethod();
};
};
Here are my questions:
How I can call firstMethod from secondMethod? Is the way I did it correct, or is better way?
How I can create a constructor for the controller? I need to call the secondMethod that call the firstMethod that initialize the sampleArray?
How I can call a specific method from html code? I found ng-initialize but I can't figure out how to use it.
You call a method the same way you declared it:
$scope.secondMethod = function() {
$scope.firstMethod();
};
Which you can also call from HTML like so:
<span>{{secondMethod()}}</span>
But controllers don't really have "constructors" - they're typically used just like functions. But you can place initialization in your controller function and it will be executed initially, like a constructor:
function exampleController($scope) {
$scope.firstMethod = function() {
//initialize the sampleArray
};
$scope.secondMethod = function() {
$scope.firstMethod();
};
$scope.firstMethod();
}
you call the first method by using $scope.
So
$scope.secondMethod = function()
{
$scope.firstMethod();
};
Not really sure what you mean in your second question.
For your third quesiton, you can either have the method run automatically "onload" on controller, OR run it via an front-end angular binding.
e.g.
Run Automatically
function exampleController($scope)
{
$scope.sampleArray = new Array();
$scope.firstMethod = function()
{
//initialize the sampleArray
};
$scope.secondMethod = function()
{
$scope.firstMethod();
};
$scope.secondMethod(); // runs automatically.
};
Run on binding
<div ng-controller="ExampleController"> <!-- example controller set up in namespace -->
<button class="btn" ng-click="secondMethod()">Run Second Method</button>
</div>
#Josh and #Christopher already covered your questions, so I won't repeat that.
I found ng-initialize but I can't know how to use that :-(
The directive is actually ng-init. Sometimes (e.g., if you are starting to use Angular in parts of an application and you still need to dynamically generate a view/HTML page server-side), ng-init can sometimes a useful way to initialize something. E.g.,
<div ng-controller="ExampleCtrl">
<form name="myForm">
<input type="text" ng-model="folder" ng-init="folder='Bob'">
Here's an example where someone needed to use ng-init: rails + angularjs loading values into textfields on edit
I'd also like to mention that controllers are not singletons. If you use ng-view, each time you go to a different route, a new controller is created. The controller associated with the view you are leaving is destroyed, and the controller associated with the view you are going to is executed. So that "initialization code" in a controller could get executed multiple times while an app is running. E.g, if you visit a page, go elsewhere, then come back, the same controller function (and its "initialization code") would be executed twice.
If you want something to truly run once, put it in a service or in a module's config() or run() methods. (Services are singletons, and hence each service is instantiated only once, so initialization code in a service is only run once.)

How can I tell AngularJS to "refresh"

I have a click event that happens outside the scope of my custom directive, so instead of using the "ng-click" attribute, I am using a jQuery.click() listener and calling a function inside my scope like so:
$('html').click(function(e) {
scope.close();
);
close() is a simple function that looks like this:
scope.close = function() {
scope.isOpen = false;
}
In my view, I have an element with "ng-show" bound to isOpen like this:
<div ng-show="isOpen">My Div</div>
When debugging, I am finding that close() is being called, isOpen is being updated to false, but the AngularJS view is not updating. Is there a way I can manually tell Angular to update the view? Or is there a more "Angular" approach to solving this problem that I am not seeing?
The solution was to call...
$scope.$apply();
...in my jQuery event callback.
Why $apply should be called?
TL;DR:
$apply should be called whenever you want to apply changes made outside of Angular world.
Just to update #Dustin's answer, here is an explanation of what $apply exactly does and why it works.
$apply() is used to execute an expression in AngularJS from outside of
the AngularJS framework. (For example from browser DOM events,
setTimeout, XHR or third party libraries). Because we are calling into
the AngularJS framework we need to perform proper scope life cycle of
exception handling, executing watches.
Angular allows any value to be used as a binding target. Then at the end of any JavaScript code turn, it checks to see if the value has changed.
That step that checks to see if any binding values have changed actually has a method, $scope.$digest()1. We almost never call it directly, as we use $scope.$apply() instead (which will call $scope.$digest).
Angular only monitors variables used in expressions and anything inside of a $watch living inside the scope. So if you are changing the model outside of the Angular context, you will need to call $scope.$apply() for those changes to be propagated, otherwise Angular will not know that they have been changed thus the binding will not be updated2.
Use
$route.reload();
remember to inject $route to your controller.
While the following did work for me:
$scope.$apply();
it required a lot more setup and the use of both .$on and .$broadcast to work or potentially $.watch.
However, the following required much less code and worked like a charm.
$timeout(function() {});
Adding a timeout right after the update to the scope variable allowed AngularJS to realize there was an update and apply it by itself.

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