user-page.component.ts

import { Component, OnInit } from '@angular/core';
import { UserService } from '../services/user.service';
import { User } from '../models/user';
import { ActivatedRoute, ParamMap } from '@angular/router';
import { Observable, BehaviorSubject } from 'rxjs';

@Component({
  selector: 'app-user-page',
  templateUrl: './user-page.component.html',
  styleUrls: ['./user-page.component.css']
})
export class UserPageComponent implements OnInit {

  user$: Observable<User>;
  userId:number = null;
  subscriptionUserId$;
  subscriptionUser$;

  constructor(public userService:UserService, private route: ActivatedRoute) {
    this.subscriptionUserId$ = this.route.paramMap.subscribe((params : ParamMap)=> {
      this.userId = parseInt(params.get('userId'));
    });
  }

  ngOnInit() {

    this.user$ = this.userService.getUserById(this.userId);

  }

  ngOnDestroy(){

    if(this.subscriptionUserId$)
      this.subscriptionUserId$.unsubscribe();

    if(this.subscriptionUser$)
      this.subscriptionUser$.unsubscribe();

  }
}