Angular Dependency Injection
Dependency Injection (DI) is a software design pattern that deals with how components get hold of their dependencies.
The AngularJS injector subsystem is in charge of creating components, resolving their dependencies, and providing them to other components as requested.
Using Dependency Injection
Dependency Injection is pervasive throughout AngularJS. You can use it when defining components or when providing run and config blocks for a module.
Services, directives, filters, and animations are defined by an injectable factory method or constructor function, and can be injected with “services”, “values”, and “constants” as dependencies.
Controllers are defined by a constructor function, which can be injected with any of the “service” and “value” as dependencies, but they can also be provided with “special dependencies”. See Controllers below for a list of these special dependencies.
The run method accepts a function, which can be injected with “services”, “values” and, “constants” as dependencies. Note that you cannot inject “providers” into run blocks.
The config method accepts a function, which can be injected with “providers” and “constants” as dependencies. Note that you cannot inject “services” or “values” into configuration.
The provider method can only be injected with other “providers”. However, only those that have been registered beforehand can be injected. This is different from services, where the order of registration does not matter.
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