How to fix Angular Service ngOnInit() not being called

Problem:

You have an Angular service implementing OnInit:

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

@Injectable()
export class MyService implements OnInit {

  constructor() { }
  
  ngOnInit() {
    console.log("MyService initializing");
  }
}

but it never prints MyService initializing – i.e. the ngOnInit() function is never actually being called.

Solution:

Services should not implement OnInit, the function is deliberately never called. Instead, add the code from ngOnInit() in the constructor() and remove implements OnInit and ngOnInit():

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

@Injectable()
export class MyService {

  constructor() {
    console.log("MyService initializing");
  }
  
}