Angular http 请求无法正常工作

Question

Angular 让我疯狂。

我有两个按钮。如果我点击第一个，我想提出这个请求:

https://localhost:44373/api/events

如果我点击第二个，我想发出那个请求:

https://localhost:44373/api/events/1

将调用“getNextPost()”方法，它似乎可以工作，但在服务器端将不会调用指定的方法。

这是我的客户端实现:

 export class AppComponent implements OnInit {
  title = 'EventsPresenter';
  _hubconnection : signalR.HubConnection;

  _notification : string = '';

  displayedColumns: string[] = ['eventDateTime', 'nbr', 'element', 'parent', 'stateTypeTitle', 'enumValueTitle', 'customerObject'];

  ROOT_URL = 'https://localhost:44373/';
  ROOT_API_URL = this.ROOT_URL + 'api/';
  dataSource: Observable<EventData[]>;
  dataSource2: Observable<EventData>;

  constructor(private http: HttpClient) {}

  getPosts(){
    this.dataSource = this.http.get<EventData[]>(this.ROOT_API_URL + 'events')
  }

  getNextPost(){
    this.dataSource2 = this.http.get<EventData>(this.ROOT_API_URL + 'events/1')
  }


  ngOnInit() {

    this._hubconnection = new signalR.HubConnectionBuilder() 
    .configureLogging(signalR.LogLevel.Trace) 
    .withUrl('https://localhost:44373/notify') 
   .build(); 

    this._hubconnection
      .start()
      .then(() => console.log('Connection Started'))
      .catch(err => console.log('Error while establishing connection'));

      this._hubconnection.on('BroadcastMessage', (data: EventData) => {    
        console.log(data);
        this.dataSource.subscribe(v => v.push(data));
      });

  }
}

这是我的服务器实现:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using convisAPI.DataProvider;
using convisAPI.Interfaces;
using EntityLibrary;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.SignalR;

namespace convisAPI.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class EventsController : ControllerBase
    {
        //EventDataProvider eventDataProvider;

        IEventDataRepository _eventDataRepository;

        IHubContext<NotifyHub> _hubContext;

        public EventsController(IEventDataRepository eventDataRepository, IHubContext<NotifyHub> hubContext)
        {
            _eventDataRepository = eventDataRepository;
            _hubContext = hubContext; 
        }

        // GET api/events
        [HttpGet]
        public async Task<ActionResult<IEnumerable<EventSummary>>> Get()
        {
            return await _eventDataRepository.GetEvents();
        }

        // GET api/values/5
        [HttpGet("{id}")]
        public async Task<ActionResult<EventSummary>> Get(int id)
        {

            Random r = new Random();

            var ra = r.Next(212, 220);

            await _hubContext.Clients.All.SendAsync("BroadcastMessage", new EventSummary()
            {
                Element = "Mein Element " + ra,
                Details = "Das ist mein Eventgrund",
                EventID = Guid.NewGuid(),
                ElementID = Guid.NewGuid(),
                EventDateTime = DateTime.Now,
                Nbr = ra,
                StateNbr = ra,
                EnumValueTitle = "Störung",
                StateEnumValue = 110 + ra
            });


            return new EventSummary();



        }

        // POST api/values
        [HttpPost]
        public void Post([FromBody] string value)
        {
        }

        // PUT api/values/5
        [HttpPut("{id}")]
        public void Put(int id, [FromBody] string value)
        {
        }

        // DELETE api/values/5
        [HttpDelete("{id}")]
        public void Delete(int id)
        {
        }
    }
}

我知道代码“Get(int id)”对您来说可能看起来很奇怪，但我基本上想触发 SignalR 通知。

有什么想法吗？

最好的问候

Answer 1

在 Angular 中，每个 HTTP 请求只会在有人收听它们时“触发”。

因此，如果没有人订阅，则不会有任何 http 请求。

getPosts(){
    this.http.get<EventData[]>(this.ROOT_API_URL + 'events')
         .subscribe(result => this.dataSource = result)
}

getNextPost(){
    this.http.get<`EventData>(this.ROOT_API_URL + 'events/1')
        .subscribe(result => this.dataSource2 = result)
}

我会写得有点不同，但那是个人风格而不是

getPosts(){
   this.dataSource = this.http.get<EventData[]>(this.ROOT_API_URL + 'events')
 }

我会写

getPosts():Observable<EventData[]>{
   return this.http.get<EventData[]>(this.ROOT_API_URL + 'events')
}

然后我会在需要数据的时候订阅。

...
this.getPosts().subscribe(result => this.isWhereINeedit = result)

亲切的问候