Angular practice - using scope inheritance vs injection

Question

I have a question that came up in a meeting that I would like to get some expert opinion on. lets say I have a 'userService' that many controllers in my app need. (in fact most of them).

It was my belief that any parent controllers would inject this userService and expose properties of that service to child controllers. Since any 'child' controllers have access to parent scope, there is no need to inject the 'userService' into every controller.

Another person's opinion was to inject the 'userService' into every controller that needs it, regardless if the service is already inherited from it's parent, basically because it makes the code easier to read and easy to find where your variables are coming from.

To me, this view seems wrong, and misses the point of Angular and how it uses prototype inheritance, and the power of scope. Doesn't this actually create unnecessary instances in memory that reference the same thing ? why would you want to do that ?

I would love to hear some experience opinions on this. Thanks!

Jeff Hubbard · Accepted Answer · 2014-05-14 15:56:14Z

2

The references in memory are cheap. Don't worry about those. More importantly, you're implicitly creating a dependency that leads to a non-reusable component when you put something on scope that a child needs to do its' job. You should instead declare your dependencies upfront--via the argument list. You'll thank yourself later when you come to testing. Scope inheritance is for templates--not controllers.

answered May 14, 2014 at 15:56

Jeff Hubbard

9,9123 gold badges33 silver badges29 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

29er Over a year ago

all good comments guys, thanks! you have made me a little smarter : )

Jonathan Rowny · Accepted Answer · 2014-05-14 15:55:32Z

1

There's some arguments both ways, but I avoid scope inheritance whenever possible. I even isolate scopes on most of my directives. The reason is that you can more naturally de-couple and encapsulate your code. Encapsulation is less of a problem on controllers in general, but it's nice to know that wherever you are in a scope hierarchy you can always get to your service.

answered May 14, 2014 at 15:55

Jonathan Rowny

7,5981 gold badge21 silver badges26 bronze badges

Comments

PaReeOhNos · Accepted Answer · 2014-05-14 15:58:12Z

Someone can correct me if I'm wrong, but I think it works like this.

Controller A injects service A. It can access it via A.method Controller B inherits from Controller A but cannot access service A as it doesn't know what it is.

Scope inheritance comes into play when you assign that service to a scope variable. If we change it now so that Controller A sets $scope.A = A THEN Controller B will be able to access the service via $scope.A.method as it has inherited this.

I don't think the injected services themselves are inherited.

In terms of memory, I wouldn't worry too much. Angular won't be creating a new instance, just a reference to it. Services are singletons and won't get recreated unless they're destroyed. If you're using Factories, then you may get new objects but that's different.

Collectives™ on Stack Overflow

Angular practice - using scope inheritance vs injection

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related