AngularJS dynamically inject scope or controller

Question

Is it possible to inject scope or controller during running ? or any other advice to dynamically inject services into controller ?

Application.controller('IndexController', function($scope){

    // some actions

    if(someconditions) {
            $scope.$inject = [someServiceName];
            // and here i want to use service methods 
    }

});

Thanks in advance

The problem is i don't know what kind of service i'll receive after actions happened before. thats why i'm confused, any advice in this case ? — Mass
– Mass, Commented Jan 19, 2013 at 15:41

Mark Rajcok · Accepted Answer · 2013-02-06 16:27:28Z

62

A service can be dynamically injected (by name) into a controller using the $injector. Being able to inject services via controller arguments is just a convenience that Angular provides. Under the hood, the $injector is used by Angular to retrieve object instances. But we can use the $injector ourselves also.

function MyCtrl($scope, $injector) {
  $scope.doSomething = function(someService) {
    var service = $injector.get(someService)  // someService contains the name of a service
    service.value += 10
}

Fiddle.

edited Feb 6, 2013 at 16:27

answered Jan 19, 2013 at 20:11

Mark Rajcok

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9 Comments

Joe Dyndale Over a year ago

Huh. OK. I stand corrected. But what is the benefit of this (besides not having a mile long arguments list)?

Liviu T. Over a year ago

I would caution against over use of the $injector. Having a visible list of dependencies tells me how much work is my controller doing and might force me to split the work

Chris Seufert Over a year ago

Use case for me is for wrapping REST API. Each 'model' type can return related items of other types, so you need to be able to dynamically select the correct service to represent the REST API relatives.

HeberLZ Over a year ago

One huge advantage of this approach is when you have a common public interface between a set of services, where you only need to execute 1 service depending on a condition. Instead of having 100 dependencies just in case you have to execute one of those services, you can inject it by name on the fly

Mark Rajcok Over a year ago

@Shashank, it came up just now when I tried it. If that link doesn't work for you, try jsfiddle.net/vaANv/98

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MechanicalCoder · Accepted Answer · 2015-04-23 12:45:28Z

4

Following is one use case i came across recently, I was trying to inject the a service "myService" in the Factoy and got the following error.

**Uncaught Error:** *[$injector:cdep] Circular dependency found: $http <- $modal <- myService <- interceptorFactory <- $http <- $templateRequest <- $compile*

[http://errors.angularjs.org/1.3.0/$injector/cdep?p0=%24http%20%3C-%20%24mod%E2%80%A6orFactory%20%3C-%20%24http%20%3C-%20%24templateRequest%20%3C-%20%24compile][1]

To solve this issue, $injector came as life saver

var service = $injector.get('myService') //this will create a dynamic service instance

and now you can use the service in a similar way you have used other services in your application.

edited Apr 23, 2015 at 12:45

answered Apr 23, 2015 at 9:56

MechanicalCoder

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2 Comments

mikermcneil Over a year ago

I cannot emphasize enough how good this answer is. The rest of our team and I spent almost a week coming up with various solutions to work around the circular imports/dependencies issue (for a case where it isn't even a logical restriction: factories that return stateless helper functions). Importing $injector and calling e.g. var someImportMakingAngularDizzy = $injector.get('someImportMakingAngularDizzy') solved all of that in about 15 minutes. Thank you!

MechanicalCoder Over a year ago

I am glad, it helped you and your team.

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