Method overloading in Angular 4 / 2

Question

I am now working with Angular 4. I have not found any proper solution about method overloading in Angular 2 or 4. Is it possible to implement method overloading in an angular service class? Or I am interested to know details about it. Thanks in advance.

I have just tried to crate Service like below but found Duplicate function implementation error

ApiService.ts :

import { Injectable } from '@angular/core';

@Injectable()
export class ApiService {
 
       constructor() { }

       postCall(url, data, token) { // with three parameters
                 return resultFromServer; }        

       postCall(url, data) { // with two parameters
                return resultFromServer;}          
       }
          
  

AuthenticationService.ts:

import { Injectable } from '@angular/core';
import { ApiService } from "app/_services/api.service";
import FunUtils from "app/_helper/utils";

@Injectable()
export class AuthenticationService {
    
    constructor(private api: ApiService) { }

    rest_login_call(userName, password) {
        let data = { username: userName, password: password };
        let url = "http://localhost:8000";
        return this.api.postCall(url, data);
    }

}

Answer 1

Instead of overloading methods, make the token parameter optional.

postCall(url, data, token?) { // with three parameters
             return resultFromServer; 
}        

Hope it helps

Answer 2

As of TypeScript 1.4, you can typically remove the need for an overload using an optional parameter and union type(if you don't know the type of the param). The above example can be better expressed using:

postCall(url: string, data: Object, token?: string | number) {
   return resultFromServer; 
}