Is it advisable to store data in $rootScope.
I have a cordova app which uses sensor data which is coming every 100ms. For me to use that data in multiple controller I am using $rootScope.sensorData variable which is being refreshed every 100ms. Is it alright to use it this way? Is there a better way to do it?
Thank you
You can store it in factory. In AngularJS factory is singleton, so only instance is created.
myApp.factory('SensorSrv', function SensorSrv() {
var sensorData;
return {
setData: setData,
getData: getData
};
function setData(data) {
sensorData = data;
}
function getData() {
return sensorData;
}
});
You can also user local-storage if you want to persist the data.
I think this is not good idea to use $rootScope in entire code logic , There are lot of reasons behind that ... Instead of that you can create code login in services it is more flexible ... and also you can see this link
Best practice for using $rootscope in an Angularjs application?
From the Official Docs:
$rootScope exists, but it can be used for evil
Scopes in Angular form a hierarchy, prototypally inheriting from a root scope at the top of the tree. Usually this can be ignored, since most views have a controller, and therefore a scope, of their own.
Occasionally there are pieces of data that you want to make global to the whole app. For these, you can inject $rootScope and set values on it like any other scope. Since the scopes inherit from the root scope, these values will be available to the expressions attached to directives like ng-show just like values on your local $scope.
Of course, global state sucks and you should use $rootScope sparingly, like you would (hopefully) use with global variables in any language. In particular, don't use it for code, only data. If you're tempted to put a function on $rootScope, it's almost always better to put it in a service that can be injected where it's needed, and more easily tested.
Conversely, don't create a service whose only purpose in life is to store and return bits of data.
--AngularJS Miscellaneous FAQ
I recommend using app.value app.value('test', 20);
Because by using $rootScope you are exposing that value to all the services which might be a security threat. By using value you can make sure where do you want to use that variable according to your requirement.
Related
I am beginning my development in angular and I don't know much. What I'm trying to do is that I am trying to pass a fairly large collection of data from one controller to another. This is how I managed to do it.
angular.module("myApp").controller("controllerName", function($rootScope, $scope, *...other stuff...*)
{ /* code */ }
Later there is one specific method which is accessed from outside, and I copy the collection like this:
$rootScope.selectedItems = angular.copy($scope.selected.items);
(This is an array of 5k strings)
Which is then catched in another controller. Other developers said it is unsafe to pass this through $rootScope but after the data is passed and copied into local controller, I use this to get rid of the collection in rootScope
delete $rootScope.selectedItems;
Is this a safe way to do this? It works perfectly, and nothing seems dangerous to me
As a general rule, don't use $rootScope to pass data. By using it you make your module dependent on unspecified functionality which may not be a dependency of your module. It's a structural issue which will create problems later.
Instead, use a service:
angular.module("myApp").service("myAppService", function () {
this.selectedItems = [];
});
angular.module("myApp").controller("controllerName1", function(myAppService, $scope) {
$scope.selectedItems = myAppService.selectedItems;
});
angular.module("myApp").controller("controllerName2", function(myAppService, $scope) {
$scope.selectedItems = myAppService.selectedItems;
});
It's also recommended that all your logic goes into services (and factories/providers where appropriate). Controllers should be used only to expose service functionality, unless a necessary special case can be proven. This makes the logic in services easier to unit test.
There are many service are available you should go with broadcast
Here is example for $broadcast service
https://toddmotto.com/all-about-angulars-emit-broadcast-on-publish-subscribing/
We have a large Angularjs 1.6 application that has $rootscope scattered throughout the app in over 200 places in filters, services, routes, etc.. so it needs to be refactored, but I'm not sure how to know when to remove it. When is it a best practice to use $rootscope in the application?
I've read everything from never, to using it for storing variables, which I assumed was for sharing data between controllers. I've since read that it's better to use factories/services for this use case instead and I also read that one valid use case is to use $rootscope as a global event bus.
I didn't really see this explained in the Angularjs docs.
From ng-book:
When Angular starts to run and generate the view, it will create a binding from the root ng-app
element to the $rootScope. This $rootScope is the eventual parent of all $scope objects.
The $rootScope object is the closest object we have to the global context in an
Angular app. It’s a bad idea to attach too much logic to this global context, in the
same way that it’s not a good idea to dirty the JavaScript global scope.
You are right, you should definitely use Services to share data and logic between your modules.
Putting a lot of logic in your $rootScope means having bad maintainability and modularity in your application, it is also very difficult to test issues.
I highly suggest you to take a look at:
Services AngularJS Documentation
Thinkster brilliant article on how to share data between controllers
Screencast by Simpulton
#Breck421 answer to this question
I know it may be easy to attach everything to $rootScope, but It is just difficult to work on it, make little changes, reusing your code for other applications or modules and test your application in general.
EDIT
Recently I had to fetch some items from API and catch these items in order to show them in a certain view. The item fetching mechanism was in a certain Factory, while the mechanism to format and show the items was in a Controller.
So, I had to emit an event in the Factory when items got fetched and catch this event in the Controller.
$rootScope way
//Factory
$rootScope.$broadcast('refreshItems', items);
//Controller
$scope.$on('refreshItems', doSomething());
It clearly worked but I didn't really like to use $rootScope and I've also noticed that the performance of that task were pretty miserable.
Then I tried giving a shot to Postal.js:
Postal.js is an in-memory message bus - very loosely inspired by AMQP -
written in JavaScript. Postal.js runs in the browser, or on the server
using node.js. It takes the familiar "eventing-style" paradigm (of
which most JavaScript developers are familiar) and extends it by
providing "broker" and subscriber implementations which are more
sophisticated than what you typically find in simple event
emitting/aggregation.
I tried using Postal.js for this kind of needs and I found out that it is really faster than using $rootScope for this purpose.
//Factory
$scope.$bus.publish({
channel : 'reloadItems',
topic : 'reloadItems'
data : items
);
//Controller
$scope.$bus.subscribe({
channel : 'reloadItems',
topic : 'reloadItems',
callback : function () {
resetAndLoadItems();
}
});
I hope I've been helpful.
From Angluar docs: Every application has a single root scope. All other scopes are descendant scopes of the root scope. Scopes provide separation between the model and the view, via a mechanism for watching the model for changes.
Of course this is going to come down to a matter of opinion and style. I tend to follow a style very close to John Papa's Angular Style Guide.
In keeping with the two, and following a good separation of concerns strategy my architecture contains factory models that are shared across the application. My controllers in turn are all bound to the services that hold the shared data.
Using $rootScope as the global event bus is exactly how Angular uses it. Should you tag along and do the same? I don't see why not. But if you are, make sure that the purpose is clearly defined and maybe even use your own service to register events to the global event bus. That way you are decoupling your app from Angular, and if you ever decide that you want to change the framework in which your global event bus lives then you can change it in one place.
This is what I'm suggesting:
Global event bus
// Angular specific: add service to module
angular.module('app').factory('globalEventBus', GlobalEventBus);
// Angular specific: inject dependencies
GlobalEventBus.$inject(['$rootScope']);
// Non framework specific.
// param: fameworkEventBus will be $rootScope once injected
function GlobalEventBus(fameworkEventBus) {
var globalEventBus = this;
globalEventBus.registerEvent(params...){
fameworkEventBus.
}
return globalEventBus;
}
Global data models
My data models are smart and tend to contain functions that provide information about themselves or retrieve/return specific data.
// Angular specific: add service to module
angular.module('app').factory('dataModel', DataModel);
function DataModel() {
var dataModel= this;
dataModel.myData = {};
dataModel.GetSpecificData = funtion(param){
return ...
}
return dataModel;
}
The controller
// Angular specific
angular.module('app').controller('MyController', MyController);
// Angular specific: inject dependencies to controller
MyController.$inject = ['dataModel'];
// By convention I use the same parameter name as the service.
// It helps me see quickly if my order of injection is correct
function MyController(dataModel) {
var myController = this;
// Bind to the service itself, and NOT to the service data property
myController.myData = dataModel;
myController.doStuff = function(){
}
}
Here is a fun post about binding to services and not to service properties.
All in all you have to be the judge of what works best for you. A good system architecture and good style have saved me countless hours of solving completely avoidable problems.
After doing some more work with Angular and more reading I found this basic rule of thumb for using $rootscope that I wanted to add to the other answers:
Only add properties that are static or constant. Anything else that
represents a changing state or a mutable value should have a
corresponding directive or controller to handle it.
If the right way to share data between controllers are using factory/service, what is the purpose of the $rootScope?
$rootScope exists, but it can be used for evil
Scopes in Angular form a hierarchy, prototypally inheriting from a root scope at the top of the tree. Usually this can be ignored, since most views have a controller, and therefore a scope, of their own.
Occasionally there are pieces of data that you want to make global to the whole app. For these, you can inject $rootScope and set values on it like any other scope. Since the scopes inherit from the root scope, these values will be available to the expressions attached to directives like ng-show just like values on your local $scope.
Of course, global state sucks and you should use $rootScope sparingly, like you would (hopefully) use with global variables in any language. In particular, don't use it for code, only data. If you're tempted to put a function on $rootScope, it's almost always better to put it in a service that can be injected where it's needed, and more easily tested.
Conversely, don't create a service whose only purpose in life is to store and return bits of data.
-- AngularJS FAQ
As per my understanding.
you can use $rootScope in multiple places .
global settings defined in factory and then in view you can update as per your condition. f.x layout manipulation
you can assigned $state on run.
you can handle error ($rootScope.$on(...)
I hope this will help.
Thanks
About shared state between controllers. I have a hard time finding the right way to do this from all the possible solutions recommended on SO. I made this sketch to illustrate the basic idea I had about this so far using a factory.
There is the factory myFactory, that holds a shared variable sharedVar.
The controllers Ctrl1, Ctrl2, Ctrl3 want to access always the updated version. They also can call an updateViaHttp.
Is that the right purpose of a factory? (in general to share state,
specific to the other options like service and provider)
If so, how to watch changes of the sharedVar in a proper way? (by
reference of objects, $watch, events (broadcast, on), ...)
Is there a general pattern that works well for objects, arrays and
primitives.
You've got the basic idea right, assuming by 'factory' you mean 'service' -- it's kind of confusing, I know, because services are declared using factory functions. That said, it's an important distinction to make so that you'll have an easier time finding documentation, etc.
Watch changes either just by using object references and being careful about watch depths in Angular (my preferred method) or by explicitly registering $watch statements (still be careful about watch depths). Generally I'm of the opinion that you shouldn't overuse broadcasts as it can make your code a little messy. It also kind of defeats the point of the service in this case, which is to be the source of shared state.
My general pattern for creating services is to bind everything I want to use to an object (both data and functions) and then return that object in the factory function. Sometimes you have to introduce some extra nesting so that the Javascript prototypical inheritance doesn't mess with you (see the watch depths thing again) but that's the general idea.
An example service for your set up:
angular.factory('shareAndUpdate', ['dependencyInjection', function(dependency) {
var srvc = {};
srvc.sharedVar = 'something';
srvc.updateViaHttp = function(){ something };
return srvc;
}]);
factories vs services vs providers - only differences are related to how the Dependency Injector provides instances of them to you. Services are specifically designed for providing singletons, but are just a wrapper over factories that add the singleton specific functionality. Nothing stopping you from returning a singleton from a factory.
using services to share state - you need a singleton and a service makes defining and injecting singletons easy.
SomeService:
var foo = {
bar = 'a';
};
function getFoo() {
return foo;
}
SomeController[SomeService injected here] :
$scope.foo = SomeService.getFoo();
$scope.$watch('foo.bar', ...);
$scope.setFooBar = function(val) {
$scope.foo.bar = val;
};
2
The general pattern here is to never do a
$scope.foo = { bar: 'Some other reference' }; because then all your other things depending on SomeService will not get the new reference when you overwrite it - the "infamous" always use a "dot" in $scope stuff issue.
You are probably looking for something like a pubsub service:
https://www.npmjs.com/package/angular-pubsub
However, in my experience, through proper design, you can minimize the necessity to share data in between non-nested controllers.
Sometimes it is unavoidable, though, for stuff like login credentials, permissions, stuff that is all-app-encompassing. In such occasions you can use a service to indeed share/get the state in between controllers, or you can go for the fully-fledged pubsub mechanism.
A factory is just another way of specifying a service. A factory, when called, gives an instance of a service. This service you can use for everything that you want, one of those things being sharing state in between your controllers.
You can watch a shared variable in many ways, the easiest being inheriting scopes, but, as you mentioned, sometimes your controllers don't necessarily inherit their scopes. Then you can use a pubsub service or just broadcast events on a shared scope for both controllers (like $rootScope, which is the parent of all controllers' scopes for your app).
If you were to use an existing pubsubservice, it would still be up to your implementing controllers to actually do the subscribe and watching on a specific variable and updating their corresponding scopes accordingly. However, that can be avoided if you design your app in such a way that your controllers inherit the variable from a shared scope. Then they will automatically update their stuff using the normal angular mechanism. That, sadly, can not always be achieved and then what you are left with is having to implement a pubsub service.
Is it correct to pass the "current" $scope to an AngularJS service?
I'm in the situation where I've a $service knowing it's consumed by only one controller, and I'd like to have a reference to the controller's scope in the $service methods themselves.
Is this philosophically correct?
Or I'd better to broadcast events to the $rootScope and then make my controller listen to them?
To let the controller know when something async happens, use Angular promises.
To provoke the $apply, you don't need the scope, you can call $rootScope.$apply, as there is no difference calling it in a specific scope or in the root.
Regarding the variable reading, it would be better if you received parameters. But you could also read it from a scope as an object parameter, but I would go with parameter, that would make your service interface much more clearer.
I would say if your functionality is specific to one controller only than you don't need a service.
The controllers tasks is to manipulate the specific model whereas a service should deal with global tasks. I would rather stick to this paradigm instead of mixing things up.
This is what the docs say
Service
Angular services are singletons that carry out specific tasks common to web apps
Controller
In Angular, a controller is a JavaScript function(type/class) that is used to augment instances of angular Scope, excluding the root scope.
PS: Apart from that if you need to digest you can also inject the $rootScope within your service.
Yes. You can pass the $scope into the service when you initialize it. In the service constructor you can assign the scope to something like this._scope and then reference the scope within the service!
angular.module('blah').controller('BlahCtrl', function($scope, BlahService) {
$scope.someVar = 4;
$scope.blahService = new blahService($scope);
});
angular.module('blah').factory('blahService', function() {
//constructor
function blahService(scope) {
this._scope = scope;
this._someFunction()
}
//wherever you'd reference the scope
blahService.prototype._someFunction = function() {
this._scope['someVar'] = 5;
}
return blahService;
});
I personally believe that passing the whole $scope to a service is a bad idea, because it creates a kinda circular reference: the controller depends on the service and the service depends on the scope of the controller.
On top of being confusing in terms of relations, things like this one end up getting in the way of the garbage collector.
My preferred approach is to put a domain object in the controller scope and pass that to the service. This way the service works regardless whether it's used inside a controller or maybe inside another service in the future.
For example, if the service is supposed to push and pop elements from an array errors, my code will be:
var errors = [];
$scope.errors = errors;
$scope.myService = new MyService(errors);
The service interacts then with the controller by operating on errors.
Of course I've got to be cautious about never wiping out the whole array reference, but at the end of the day that's a general JS concern.
I'd never want to use broadcasting, $apply and/or similar things, because imho good OO-practices will always trump whatever Angular-magics.