Angular - Generic type 'Observable<T>' requires 1 type argument(s). - Solved

Now, let's see article of Angular Generic type 'Observable' requires 1 type argument(s). you'll learn angular 13 Generic type 'Observable' requires 1 type argument(s). Here you will learn Angular Generic type 'HttpRequest' requires 1 type argument(s).ts solved. i explained simply about Angular Generic type 'Observable' requires 1 type argument(s).

Few days ago i was working on my angular 13 application and i created post service file and i used Observable with function as like bellow:

getAll(): Observable {
  
    return this.httpClient.get(this.apiURL + '/posts/')
  
    .pipe(
      catchError(this.errorHandler)
    )
}

Then i run app and got error like bellow:

Then i research on google and find out solution with should be a concrete type complex or primitive. so let's see solution:

Solution: Pass concrete type <any>

getAll(): Observable<any> {
  
    return this.httpClient.get(this.apiURL + '/posts/')
  
    .pipe(
      catchError(this.errorHandler)
    )
  }

Now it will works.

Now my working service full code is bellow:

Full Service:

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';
       
import {  Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';
    
import { Post } from './post';
    
@Injectable({
  providedIn: 'root'
})
export class PostService {
  
  private apiURL = "https://jsonplaceholder.typicode.com";
  
  /*------------------------------------------
  --------------------------------------------
  Http Header Options
  --------------------------------------------
  --------------------------------------------*/
  httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json'
    })
  }
  
  /*------------------------------------------
  --------------------------------------------
  Created constructor
  --------------------------------------------
  --------------------------------------------*/
  constructor(private httpClient: HttpClient) { }
  
  /**
   * Write code on Method
   *
   * @return response()
   */
  getAll(): Observable<any> {
    return this.httpClient.get(this.apiURL + '/posts/')
    .pipe(
      catchError(this.errorHandler)
    )
  }
  
  /**
   * Write code on Method
   *
   * @return response()
   */
  create(post:Post): Observable<any> {
    return this.httpClient.post(this.apiURL + '/posts/', JSON.stringify(post), this.httpOptions)
    .pipe(
      catchError(this.errorHandler)
    )
  }  
  
  /**
   * Write code on Method
   *
   * @return response()
   */
  find(id:number): Observable<any> {
    return this.httpClient.get(this.apiURL + '/posts/' + id)
    .pipe(
      catchError(this.errorHandler)
    )
  }
  
  /**
   * Write code on Method
   *
   * @return response()
   */
  update(id:number, post:Post): Observable<any> {
    return this.httpClient.put(this.apiURL + '/posts/' + id, JSON.stringify(post), this.httpOptions)
    .pipe(
      catchError(this.errorHandler)
    )
  }
     
  /**
   * Write code on Method
   *
   * @return response()
   */
  delete(id:number){
    return this.httpClient.delete(this.apiURL + '/posts/' + id, this.httpOptions)
    .pipe(
      catchError(this.errorHandler)
    )
  }
    
  /**
   * Write code on Method
   *
   * @return response()
   */
  errorHandler(error:any) {
    let errorMessage = '';
    if(error.error instanceof ErrorEvent) {
      errorMessage = error.error.message;
    } else {
      errorMessage = `Error Code: ${error.status}\nMessage: ${error.message}`;
    }
    return throwError(errorMessage);
 }
}

I hope it can help you...