:point_right: Make sure to first read the introduction to dependency injection and the @inject documentation.

Registers a method as an injection handler, allowing it to fulfill injections explicitly. It is essentially a more powerful alternative to @injectable.


Where targetType can be any class.

May be applied to a static method to handle injections for the targetType directly. The method return a value compatible to the given type or null/undefined to leave the injection unhandled. The method is also passed an Injection object of the following type:

  type: Class,
  injector: Injector,
  param: object | string | number | boolean | null


  • type is the exact type that was requested. May be identical to the type parameter of the decorator, or another compatible class.
  • injector is the Injector instance the injection handler is registered with. May be used to create or resolve other objects.
  • param is an injection parameter that may have been passed via @inject(param) or resolve(type, param).


import {injectionHandler, Injection} from 'tabris-decorators';

class MyInjectionHandler {

  static handleInjection(injection: Injection) {
    return new Foo();


If no compatible value is returned the next injection handler is called. If no injection handler returns a compatible value the injection fails. (@injectable implicitly creates an injection handler.) A single class may hold any number of injection handler methods. The name of an injection handler methods is not relevant.

@injectionHandler({targetType, priority?})

Where targetType can be any class and priority - if given - has to be a number.

Like @injectionHandler(targetType), but allows to give a priority, just like @injectable({priority}). The priority controls in which order injection handlers for the same target type are called, with the highest priority handler being called first.