你如何使用 Observable.bindCallback()

Question

如何将Observable.bindCallback() 与返回2 个参数callback(results, status) 的回调一起使用？该示例使用下面的google.maps.places API：

  const service = new google.maps.places.PlacesService(map);
  // service.nearbySearch(request, callback);


  function callback(results, status) {
    if (status === google.maps.places.PlacesServiceStatus.OK) {
      for (var i = 0; i < results.length; i++) {
        createMarker(results[i]);
      }
    }
  }

我想做这样的事情：

const handleError = err=>console.error(error);

const nearbyAsObservable = Observable.bindCallback(service.nearbySearch)
nearbyAsObservable(request)
   .subscribe( 
     (results,status)=>{
       if (status!="OK") handleError(results);
       callback
     }
     , handleError
   )

但我不确定以下几点：

1) 是从next 处理程序中“抛出”错误并在error 处理程序中捕获它的最佳做法，或者只是调用方法handleError()？

2) 我收到Cannot read property 'nearbySearch' of undefined(…) 错误。但是当我打电话给const nearbyAsObservable = Observable.bindCallback( service.nearbySearch.bind(service) ) 时，我得到一个 TS 错误：

// const nearbyAsObservable = Observable.bindCallback(service.nearbySearch.bind(service) )
// nearbyAsObservable(request)
[ts] Supplied parameters do not match any signature of call target.
const nearbyAsObservable: () => Observable<{}>

更新看起来这个 hack 将修复 TS 错误

const nearbyAsObservable : any = Observable.bindCallback(service.nearbySearch.bind(service) )
nearbyAsObservable(request)
   .subscribe( 
     (results,status)=>{
       if (status!="OK") handleError(results);
       callback
     }
     , handleError
   )

但是如果我给它(result, status)=>void，next 处理程序会抱怨

3) 如何将 Observable 返回从 Observable<[result, status]> 转换为 Observable<PlaceResult[]>？

Answer 1

答案如下：

1) 必要时将作用域绑定到您的回调（见注释）

2) 如果绑定了作用域，则使用let nearbyAsObservable : any; 修复一个TS bug how do I use `Observable.bindCallback()` with typescript

3) 使用Observable.bindCallback() 中的selector 函数将多个返回参数映射到subscribe 函数的单个响应中，并抛出错误。 How do I use the RXJS selector function in the Observable.bindCallback method?

let nearbyPlaces = function(position: google.maps.LatLng) : Observable<google.maps.places.PlaceResult[]> {  
  const service = new google.maps.places.PlacesService(map)
  // 1) bind scope
  const nearbySearchCallback = service.nearbySearch.bind(service)

  let nearbyAsObservable : any;
  // 2) type any fixes: 
  //    [ts] Supplied parameters do not match any signature of call target. 
  //    const nearbyAsObservable: () => Observable<{}>  

  nearbyAsObservable = Observable.bindCallback( 
    nearbySearchCallback        // with bound scope
    , (results, status) => {    // 3) selector function
        if (status != google.maps.places.PlacesServiceStatus.OK) throw {status, results};
        return results  
      }
  );
  const placeRequest = {
    location: position,
    radius: 25,
    rankBy: google.maps.places.RankBy.PROMINENCE,
  }
  return nearbyAsObservable(placeRequest) as Observable<google.maps.places.PlaceResult[]>
}


// usage example:
nearbyPlaces(position).subscribe(
  (results:google.maps.places.PlaceResult[])=>console.log(results)
  , err=>console.error(err)
)