You need to pass the parent injector like
export class MyIfDirective {
constructor(private injector:Injector, private _viewContainer: ViewContainerRef,
private _template: TemplateRef)
{ }
@Input() set myIf(rule: string) {
let resolvedProviders = ReflectiveInjector.resolve([AdminOnly]);
let childInjector = ReflectiveInjector.fromResolvedProviders(resolvedProviders, this.injector);
let adminOnly : IRule = childInjector.get(AdminOnly);
let show = adminOnly.shouldShowElement();
show ? this.showItem() : this.hideItem();
}
private showItem() {
this._viewContainer.createEmbeddedView(this._template);
}
private hideItem() {
this._viewContainer.clear();
}
}
See also Inject service with ReflectiveInjector without specifying all classes in the dependency tree