I just want to understand why in the following jsFiddle 'here is a lo' is printed three times.
http://jsfiddle.net/wg385a1h/5/
$scope.getLog = function () {
console.log('here is a log');
}
Can someone explain me why ? What should I change to have only one log "here is a log" (that's what I would like this fiddle do). Thanks a lot.
Angular uses digest cycles/iterations to determine when state has changed and needs to update the UI. If it finds any change on one of it's cycles, it keeps rerunning cycles until the data stabilizes itself. If it's done 10 cycles and the data is still changing, you'll see a rather know message: "angularjs 10 iterations reached. aborting".
Therefor, The fact that you are seeing the message displayed 3 times is because you have a simple interface. In fact, you can get up to many more such messages in the log, due to the fact that your directive uses {{getLog()}}. Angular keeps evaluating the expression to see if it changed.
To avoid such problems, under normal circumstances, you should store the value returned by the function you want called only once in the $scope object inside the controller and use that variable (not the function call) in the UI.
So in the controller you'd have $scope.log = getLog() [assuming it returns something, and not just writing to the console] and in the directive use the template {{log}}. This way, you'll get the value only once, per controller instance.
Hope I was clear enough.
Related
I am using angular-meteor and would like to perform a function on each object. I tried running this function within an ng-repeat in the view, but I am getting massive amounts of function calls and can't figure out why. I tried to make it as simple as possible to demonstrate what is going on.
constructor($scope, $reactive) {
'ngInject';
$reactive(this).attach($scope);
this.loaderCount = 0;
this.helpers({
loaders() {
return Loaders.find( {isloader:true}, {sort: { name : 1 } })
}
});
That gives me 26 Loaders. My function just adds 1 to the count every time the function is called:
displayLoaderCount()
{
return ++this.loaderCount;
}
Now in my view, I am looping through each loader, and calling the function. This should in my mind give me 26, but instead I am getting 3836.
<tr ng-repeat="loader in loaderExhaustion.loaders">
<td>{{loaderExhaustion.displayLoaderCount()}}</td>
Can anyone help explain this to me? Ideally I would like to loop over the contents in my module but as the collection is async, when the loop starts the length of the collection is 0, hence why I made the call in the view.
THANKS!
Every time angular enters a change detection cycle, it evaluates loaderExhaustion.displayLoaderCount(), to know if the result of this expression has changed, and update the DOM if it has. This function changes the state of the controller (since it increments this.loaderCount), which thus triggers an additional change detection loop, which reevaluates the expression, which changes the state of the controller, etc. etc.
You MAY NOT change the state in an expression like that. For a given state, angular should be able to call this function twice, and get the same result twice. Expressions like these must NOT have side effects.
I can't understand what you want to achieve by doing so, so it's hard to tell what you should do instead.
I have an AngularJS 1.4* application running locally (yet). This app is served by an Laravel 5.1 backend RESTFul API.
I have to make this app that represents a package trip. A package is composed by days, ranging from 0 to N days. Each day have a list of services, ranging from 0 to N services. And a hotel.
My web server, from which my laravel application consumes from, delivers me a pre-setted package, containing a list of days: each one with a list of services and a hotel data (unused so far). On the response I have a list of properties for the package (that don't matter for now) and an array of days, called days_info. That response is being put in the $scope.package, on my PackageController. The PackageController also declares an directive called packageBlock, that consists in a list of days, and some other data for the package.
<div ng-repeat="day in package.days_info" class='row'>
<div class='col-md-12'>
<package-days-block></package-days-block>
</div>
</div>
Inside <package-days-block> directive, I have another to iterate through the list of services inside every day.
<div class='container-fluid' ng-repeat='service in day.services' ng-controller="ServiceController">
<service-block></service-block>
</div>
That's where the problem begins: to my undestandment, I now have a $scope.service inside my ServiceController. So, I started to change it on my need inside the ServiceController through a $scope.service.
The $scope.service has an attribute called service_id. I put a listener/watcher on it, so at any time the $scope.service.service_id is changed, I ask for another service_table (holds the informations about the services, it's based on the service_id previously choosen or changed by the user), and put it in the $scope.service.table.
// ServiceController
$scope.reloadServicesTable = function(service_id, service_day, date, paxes){
MandatoryService.getServiceTable(service_id, service_day, date, paxes)
.then(
function(service_data) {
$scope.service.table = service_data;
},
...
);
The reloadServicesTable is called on the watcher for the service_id changes.
// ServiceController
$scope.$watch(
'service.service_id', // Places the watcher to watch the changes on the service's ID.
function(new_service, old_service) {
if( new_service === old_service )
return;
$scope.reloadServicesTable($scope.service.service_id, $scope.service.service_day, $scope.day.date, $scope.package.paxes);
}
);
The problem starts here: the request for the service's table is called twice when the service_id only changes once.
WHY, GOD, WHY?!
There's another part of my code where I, from the PackageController, run through the entire days_info array and reads the value of an attribute price inside the service.table: service.table.price. In there, I realise that there's two scope's: the one I handling and the other that I have no FREAKING IDEA where it came from!
If I put an console.log($scope); inside the method that runs through the days_info, I get two scopes for every request. This method is on the PackageController.
Any ideas why this is happening?
P.S.: It's my very first AngularJS application, so, take easy if I messed up on something basic...
EDIT:
As pointed out by an fellow on the comments, my question wasn't very reproducible. Sadly, I can't put here only the part I'm having doubts cause I don't have the slightest idea where the problem lies! (I know that this isn't much of help)
I took some screen shots from the Chrome Console:
First, the requestions fired on the change of the service_id
As you can see, every request is called twice everytime. This is not an one-time-thing. The /api/service/{id}... is the call for the service's table information. The /api/service/by_route/origin/... returns an list of services from one city to another (or the same). One does not interfere on the other.
The other image is the output from a console.log from the PackageController $scope, on the time that the service_id is being changed.
As you can see, there's two different scopes. And the b scope is son of the r scope. The r scope is also calling the watcher on the service_id?
The call for the sums price is been called twice from differente places, as you can see in the image below:
It may solve you issue. Even i had faced exactly the same as you are mentioning.
The reason for me was that, the controller was getting initialized again and there was a separate api call written in that, which was intended to load the page initially.
There can also be a scenario where you have assigned controller twice in the mark up.
<div ng-repeat="day in package.days_info" class='row'>
<div class='col-md-12'>
<package-days-block day="day"></package-days-block>
</div>
</div>
<div class='container-fluid' ng-repeat='service in day.services'>
<service-block service="service"></service-block>
</div>
Pass day and service down into directives. Use two way binding to pass your day and service changes back up to package.days_info.
Remove your ServiceController It does not make much sense to ng-repeat a controller. <service-block> and <package-days-block> are E directive that handle logic.
Write only one watcher in your PackageController that watch package.days_info When your day or service change, it can simply find out and do something about it.
Just Chill and fix it.
I'm pretty new to angular js and I have a question about the ng-repeat. I'm following examples at AngularJs : https://docs.angularjs.org/guide/concepts
The section that I'm currently on is 'Adding UI logic: Controllers'. If you look at the index.html, specifically at the code:
<span ng-repeat="c in invoice.currencies">
{{invoice.total(c) | currency:c}}
</span>
When I run in the browser, everything works as expected, but I notice that invoice.total function runs at least 6 times. How do I know? Well in the index.js I added a console.log function within the total function as seen here:
this.total = function total(outCurr){
console.log(outCurr)
console.log(this.convertCurrency(this.qty * this.cost, this.inCurr, outCurr))
return this.convertCurrency(this.qty * this.cost, this.inCurr, outCurr);
};
I would expect the code to run 3 times because the invoice.currencies only has 3 items:
this.currencies = ['USD', 'EUR', 'CNY'];
However, this is what I see in my browser console window:
Any ideas? Thank you in advance?
user2341963 has probably the good answer so i'll quote it first and i'll add some precision.
The digest cycle runs at least twice to check that a value hasn't
changed. First time it runs for each of the values in this.currencies.
It runs again to check that the first digest cycle hasn't changed any
values. It hasn't so it stops after the 2nd cycle
In angular you have what we call a digest cycle. This cycle watch for any change that happened in the application bind to angular. In order to refresh it. This permit to refresh your DOM when you need without refreshing the whole page.
"The bind to angular" means
Every block between {{}}
Every use of scope.$watch or attrs.$observe which are used massively by directives (ng-model/ng-repeat/...).
I don't know what makes this cycle to trigger twice at start this is probably because of some internal mechanics or the filter that you use. Check this link for more info : https://www.ng-book.com/p/The-Digest-Loop-and-apply/
I am currently building a simple drag & drop directive so that I can move some SVG stuff around on the screen. At the moment I'm still in the early stages, but I have run into a strange issue with $watch that I'm hoping someone can help me with.
I have a service that maintains my mouse state. At the moment it's just the x and y coordinates of the cursor. I also have an attribute level directive that interacts with this service in order to bind to the mouse-move event and update the service whenever someone moves the mouse around. These two items work together like a champ. The directive keeps the service up to date with the mouse's position and since my service (Factory really) is a singleton, I can pull this data in to other directives/controllers to see what's going on with the mouse.
Here's the problem: I'm trying to allow a specific SVG element to be dragged around, so I created a super simple controller with two functions: a "trackDrag" function that begins tracking and moving a specific element, and a "releaseDrag" which stops tracking/moving the element (drops it where it is, basically).
Inside of my trackDrag function, I attempt to use $scope.$watch to watch the mouse service's current x and y coordinates. Since it's a factory, these values are returned in a function and my watch looks something like this:
$scope.$watch("mouseTrackingService.get()", function(){
// do some stuff here
});
This watch DOES fire off when I first start dragging an element but it doesn't fire as I continue dragging it across the screen. In my "releaseDrag" function, I deallocate the watcher and that seems to work correctly. I'm kind of stumped about why I don't see the watch fire off continuously, even though I can console write out inside of the service and I see that IT is updating correctly.
I've included a plnkr with some sample code below:
http://plnkr.co/edit/g3WEgiQWvd9oXCpFEByn?p=preview
If I just give in and use a $interval then this code works (updating the position every 10ms for example), but really I see that as a much less "angular" way of doing things vs binding.
Ugh, I'm just being dumb. I forgot that $scope.$watch can ONLY WATCH SCOPE VARIABLES.
I fixed this issue by adding the following wrapper around the service:
$scope.currentMouse = function(){
return mouseTrackingService.get();
};
I can then watch currentMouse:
$scope.$watch(currentMouse(), function(){
updateMousePosition(target);
console.log("noticed a change");
});
Of course that gives me that awful Digest error after more than like a half second of dragging:
Uncaught Error: [$rootScope:infdig] 10 $digest() iterations reached. Aborting!
But that's a different issue entirely.
Sorry folks, nothing to see here. Move along now :-p
For some reason when getData uses angular resource to bring the data it is being called twice, causing the resource to do it REST request twice too <--- bad...
Any idea why and how to solve it?
Here a working testcase/plunker example that recreates this scenario (look at the browser console - "getData being called...." displayed twice ) b.t.w as you can see I'm not really using the resource to bring real data, just to demonstrate the scenario, In my real app I do use the resource to bring real data and its being called twice just like in this example,
Thanks ahead
After looking into the src of the ng-table I noticed the following
$scope.$watch('params.$params', function(params) {
$scope.params.settings().$scope = $scope;
$scope.params.reload();
}, true);
Which means that the tables calls it 'getData' on count/filter/group/groupBy/page/sorting
which explains the behavior I was seeing.
When you call params.count(...) you ask ng-table to refresh data as you change page size. That's why you have two get-data calls.
If you don't want to have paging, then remove calls params.count and params.total.
If you need paging, then set page size and do not change it in getData.
This happened to me with a weird reason. getData get called twice on init (first load) only. changing page or sorting didn't call getData twice. The reason was that at init the ng-table directive was hidden in the template file.
Thank #Alexander Vasilyev. I understood my problem as you said. I want to explain a litte more here. In fact, the object "params" is the object configuration the table ng-table, then if "params" changed (ex: count or a property of the object), ng-table will invoke function getData() to refresh table.
In my case, I want to get information in the object "params" and change it but I dont want to refresh ng-table. I did it by cloning object "params" et work his object copied. Clone the object in JS with jQuery :
var resultParams = jQuery.extend(true, {}, params.$params);
And then, I will work on the object resultParams instead of "params" original.