Let's perform the following steps to create a new current user service:

1. First, we'll set up our /src/app/users.ts model as a very simple model, with an extra method that will construct a full name for us from the first and last name properties:

export class User {
  constructor(
    public firstName: string = "",
    public lastName: string = "",
    public email: string = ""
  ) {}

  getName() {
    return this.firstName + ' ' + this.lastName;
  }
}

2. Next, we will set up our current user service at /src/app/current-user.service.ts. It is a very simple service that simply reads and returns our user model:

import { Injectable } from '@angular/core';
import {User} from "./user";

@Injectable()
export class CurrentUserService {
  user: User;

  getUser() {
    return this.user;
  }

  setUser(newUser:User) {
    return this.user = newUser;
  }
}

3. Angular-CLI doesn't automatically provide us with new services we generate, so we will need to manually add our new service to the provider list in /src/app/app.module.ts, as follows:

...
import { CurrentUserService } from "./current-user.service";
...

@NgModule({
  ...
  providers: [
    { provide: LOCALE_ID, useFactory: getLocaleProvider },   
    CurrentUserService
  ],
  ...
})
export class AppModule {
  constructor(private currentUserService: CurrentUserService) { }
}

4. Since our current user service doesn't self-initialize itself with a user, we will need to create one in our AppModule constructor:

...
import { CurrentUserService } from "./current-user.service";
import { User } from "./user";
...
export class AppModule {
  constructor(private currentUserService: CurrentUserService) {
    let user = new User('George','Washington','[email protected]');
    currentUserService.setUser(user);
  }
}

5. To check whether our current user service is indeed available in the rest of our application, let's add our current user's name to our /src/app/posts/create-post-form/create-post-form.component.ts modal:

import {Component, OnInit} from '@angular/core';
import {NgbModal} from '@ng-bootstrap/ng-bootstrap';
import {BlogPost} from "../blog-post";
import {CurrentUserService} from "../../current-user.service";
import {User} from "../../user";
...
export class CreatePostFormComponent implements OnInit {
  model: BlogPost;
  user: User;
  constructor(private modalService: NgbModal, private currentUserService:  
    CurrentUserService) {}
  ...
  ngOnInit() {
    this.user = this.currentUserService.getUser();
  }
}

6. Finally, we'll add the current user's full name to our modal's title header. So, now when we launch our modal, we will see New Post - by George Washington:

<ng-template #modal let-c="close">
  <div class="modal-header">
    <h4 class="modal-title">
      New Post 
      <small>- by {{user.getName()}}</small>
    </h4>
    <button type="button" class="close" aria-label="Close" (click)="c()">
      <fa [name]="'close'"></fa>
    </button>
  </div>
  ...
</ng-template>