Package dagger

Annotation Type BindsInstance

@Documented
@Retention(RUNTIME)
@Target({METHOD,PARAMETER})
@Beta
public @interface BindsInstance

Marks a method on a component builder or a parameter on a component factory as binding an instance to some key within the component.

For example:

   @Component.Builder
   interface Builder {
     @BindsInstance Builder foo(Foo foo);
     @BindsInstance Builder bar(@Blue Bar bar);
     ...
   }

   // or

   @Component.Factory
   interface Factory {
     MyComponent newMyComponent(
         @BindsInstance Foo foo,
         @BindsInstance @Blue Bar bar);
   }
 

will allow clients of the builder or factory to pass their own instances of Foo and Bar, and those instances can be injected within the component as Foo or @Blue Bar, respectively. It's important to note that unlike in factories, the methods in builders should only accept and bind a single parameter each. Using the following will result in an error:

   @Component.Builder
   interface Builder {
     // Error! Builder methods can only have one parameter
     @BindsInstance Builder fooAndBar(Foo foo, @Blue Bar bar);
     ...
   }
 

@BindsInstance arguments may not be null unless the parameter is annotated with @Nullable.

For builders, @BindsInstance methods must be called before building the component, unless their parameter is marked @Nullable, in which case the component will act as though it was called with a null argument. Primitives, of course, may not be marked @Nullable.

Binding an instance is equivalent to passing an instance to a module constructor and providing that instance, but is often more efficient. When possible, binding object instances should be preferred to using module instances.