如何在typescript中的泛型类中创建类型为'T'的新对象？

I have the following service

我有以下服务

@Injectable()
export class CollectionService<T> {    

    constructor(protected http: Http) {}

    factory<T>(item?: any): T {
        let type: new (item?: any) => T;
        return new type(item);
    }

    item(id): Observable<T> {
        return this.http.get(`${this.baseUrl}/${id}`)
            .map((resp: Response)=> this.factory(resp.json()))
            .catch((error: any) => {
                return Observable.throw(error);
            });
    }
}
@Inject