I encountered a TypeScript error when trying to make an HTTP post request using Angular

In my Angular 5 application, I am trying to interact with an API using a service. I have a method that is intended for posting data to the API. However, when I specify the type of the post method as "Candidate" object, I receive the following warning:

src/app/candidates.service.ts(17,12): error TS2558: Expected 0 type arguments, but got 1.

Here is the code for my function:

addCandidate(candidate: Candidate): Observable<Candidate> {
return this.http.post<Candidate>(this.apiUrl, candidate, httpOptions);}

I suspect that I may be misusing types in this code snippet, but I am uncertain.

angulartypescripttypeerrorangular-http

Answer №1

One potential reason for the issue could be that you are still using the outdated Http class instead of the newer HttpClient.

import {Http} from '@angular/http'; //deprecated client without generic type support
import {HttpClient} from '@angular/common/http'; //modern client with enhanced features

To resolve this, simply replace private http: Http with private http: HttpClient in your service's constructor and update the import statement for HttpClient as shown below:

import {HttpClient} from '@angular/common/http`

Additionally, make sure to add HttpClientModule to the imports array in your AppModule module like so:

//app.module.ts
import { HttpClientModule } from '@angular/common/http';

....
imports: [HttpClientModule]

Answer №2

Is it possible for the http post method to provide a candidate as a return value? If not, simply switch to Observable instead of Observable<Candidate>

Answer №3

In my opinion, it would be beneficial to exclude the <Candidate> tag from this section as the post method only requires JSON data to be sent. Furthermore, you have already specified this in your 

addCandidate(candidate: Candidate)
method parameter declaration.

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