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API > @angular/core

Self

A parameter decorator to be used on constructor parameters, which tells the DI framework to start dependency resolution from the local injector.

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Description

Resolution works upward through the injector hierarchy, so the children of this class must configure their own providers or be prepared for a null result.

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Usage notes

In the following example, the dependency can be resolved by the local injector when instantiating the class itself, but not when instantiating a child.

class Dependency {} @Injectable() class NeedsDependency { constructor(@Self() public dependency: Dependency) {} } let inj = ReflectiveInjector.resolveAndCreate([Dependency, NeedsDependency]); const nd = inj.get(NeedsDependency); expect(nd.dependency instanceof Dependency).toBe(true); inj = ReflectiveInjector.resolveAndCreate([Dependency]); const child = inj.resolveAndCreateChild([NeedsDependency]); expect(() => child.get(NeedsDependency)).toThrowError(); 
      
      
  1. class Dependency {}
  2.  
  3. @Injectable()
  4. class NeedsDependency {
  5.   constructor(@Self() public dependency: Dependency) {}
  6. }
  7.  
  8. let inj = ReflectiveInjector.resolveAndCreate([Dependency, NeedsDependency]);
  9. const nd = inj.get(NeedsDependency);
  10.  
  11. expect(nd.dependency instanceof Dependency).toBe(true);
  12.  
  13. inj = ReflectiveInjector.resolveAndCreate([Dependency]);
  14. const child = inj.resolveAndCreateChild([NeedsDependency]);
  15. expect(() => child.get(NeedsDependency)).toThrowError();