4: Add Services

[examples/angular-tour-of-heroes] / src / app / message.service.ts

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

@Injectable({
  providedIn: 'root'
})
export class MessageService {

  messages : string[] = [];

  add(message : string): void {
    this.messages.push(message);
  }

  clear(): void {
    this.messages = [];
  }
}