What is @inject actually used for?

Question

Angular

Clearly, a decorator allows dependencies to be injected into an existing class. These can be classes or individual primitives.

But why write @Inject if angular allows you to omit this keyword?

In what cases to use @Inject - can you give a good example of when this is apropos?

Answer 1

To take from the injector entities whose token is not a class constructor, but is, for example, a string or an object of type InjectionToken.
As examples - LOCAL_ID, DOCUMENT, MAT_DIALOG_DATAetc.
@Inject is always present, just for class instances where the token and its type match, this decorator can be omitted.