useExisting

Binds a DI token to an existing token.

Injector returns the same instance as if the provided token was used. This is in contrast to useClass where a separate instance of useClass is returned.

Because useExisting and useClass are often confused the example contains both use cases for easy comparison.

class Vehicle {}
 
class Car extends Vehicle {}
 
var injectorAlias = Injector.resolveAndCreate([
  Car,
  new Provider(Vehicle, useExisting: Car)
]);
var injectorClass = Injector.resolveAndCreate([
  Car,
  new Provider(Vehicle, useClass: Car)
]);
 
expect(injectorAlias.get(Vehicle) == injectorAlias.get(Car), isTrue);
expect(injectorAlias.get(Vehicle) is Car, isTrue);
 
expect(injectorClass.get(Vehicle) != injectorClass.get(Car), isTrue);
expect(injectorClass.get(Vehicle) is Car, isTrue);