* Separate applications into distinct presentation, data, and logic components

* Encourage loose coupling between these components

makes angular applications better structured, easier to maintain and more testable.

The following topics explain how angular incorporates the MVC pattern into the angular way of

The most common way to keep controllers slim is by encapsulating work that doesn't belong to

controllers into services and then using these services in controllers via dependency injection.

Services} sections of this guide.

Do not use controllers for:

with a module either via the {@link api/angular.module Module#factory api} or directly

via the {@link api/angular.module.AUTO.$provide $provide} api inside of module config function.

themselves with Angular's DI system (injector) under a `name` (id) as well as by declaring

dependencies which need to be provided for the factory function of the registered service. The

ability to swap dependencies for mocks/stubs/dummies in tests allows for services to be highly

# Dependencies

Services can not only be depended upon, but also have its own dependencies. These can be specified

in Angular and the use of array notation and $inject property to make DI annotation

minification-proof.

Services are a feature that angular brings to client-side web apps from the server side, where

services have been commonly used for a long time. Services in angular apps are substitutable

## Related Topics

## Related Topics

* {@link dev_guide.services.creating_services Creating Angular Services}

* {@link dev_guide.services.managing_dependencies Managing Service Dependencies}

* {@link dev_guide.services.testing_services Testing Angular Services}

Notice that no global variables were harmed in the writing of this test.

easy to do, but you still need to do it if you wish to take advantage of the testability story.

## Controllers