Autoinjected API - api

Question

i am developing an application using Angular2 (actually, ionic framework). Application itself contains a login form that should work via API.
Structure:
form.ts
Contains logic related to login form
import {Component, Injectable} from '#angular/core';
import { Http } from '#angular/http';
import {User} from '../../../base/user';
import {API} from '../../../base/API';
#Component({
templateUrl: 'build/pages/account/loginForm/form.html',
selector: 'login-form',
providers: [Http, API]
})
export class AccountForm {
constructor() {
...
}
submitLogin($event) {
var username = this.username.value;
var password = this.password.value;
this.user = new User(username, password);
this.user.authenticate()
}
}
user.ts
Class that contains some user information (username, password hash)
import { Inject } from '#angular/core';
import { Hash } from "./hash";
import { API } from "./API";
export class User {
public username: string;
public password: string;
public pwdhash: string;
constructor(
username: string,
password: string,
private api: API ///// problem is here
) {
let hash = new Hash();
this.username = username;
this.password = password;
this.pwdhash = hash.hash(username, password);
}
authenticate() {
var promise = this.api.loginUser({username: this.username, pwdhash: this.pwdhash});
console.log(promise);
}
}
API.ts
Class with API request to the backed
import { Http, Response, Headers, RequestOptions } from '#angular/http';
import { Injectable, Inject } from '#angular/core';
import { Hash } from './hash';
#Injectable()
export class API {
private http: Http;
constructor(#Inject(Http) http: Http) {
}
loginUser (user) {
return this.http.post(url, body, options);
}
}
What i want to do is use API class in a User.authenticate() call, but i don't want to pass it as a parameter to the User.constructor(), as this is a bad style.
Another option is to create a User.API member in a constructor, which looks ugly too.
Looks like i need just a function that makes API requests. However, i am not sure this is a good idea for Object-Oriented Programming.
Is there any way to inject API into User class without creating a new API object of this class?
Thanks