打字稿将此绑定到数组排序

Question

I am re-implementing a working JS solution into Typescript. I have an array of objects that have a Geolocation in latitude and longitudes.

I want to sort them by their distance to one particular location, currentLocation .

I would like to store currentLocation as a private attribute and access it within the sort function. However, when doing this.currentLocation , this remains undefined in compare . I tried compare.bind(this) , but no success. this is not defined .

Any ideas how to solve this problem? I solved it in JS with global variables, but that's not elegant. sortByDistance is an object method.

 sortByDistance() {

      this.currentPosition = Leaflet.latLng(this._currentLatLng[0], this._currentLatLng[1]);

      function compare(a, b) {
        let p1 = Leaflet.latLng(a.lat, a.lng);
        let p2 = Leaflet.latLng(b.lat, b.lng);

        if (p1.distanceTo(this.currentPosition) < p2.distanceTo(this.currentPosition))
          return -1;
        else if (p1.distanceTo(this.currentPosition) > p2.distanceTo(this.currentPosition))
          return 1;
        return 0;
      }
      compare.bind(this);
      this.sorted = this.objects.sort(compare);

  }

Answer 1

You can change

 function compare(a, b) {
        let p1 = Leaflet.latLng(a.lat, a.lng);
        let p2 = Leaflet.latLng(b.lat, b.lng);

        if (p1.distanceTo(this.currentPosition) < p2.distanceTo(this.currentPosition))
          return -1;
        else if (p1.distanceTo(this.currentPosition) > p2.distanceTo(this.currentPosition))
          return 1;
        return 0;
      }

with

compare = (a, b)=>{
   let p1 = Leaflet.latLng(a.lat, a.lng);
   let p2 = Leaflet.latLng(b.lat, b.lng);

   if (p1.distanceTo(this.currentPosition) < p2.distanceTo(this.currentPosition))
      return -1;
   else if (p1.distanceTo(this.currentPosition) > p2.distanceTo(this.currentPosition))
      return 1;
   return 0;
}

so that this will be in lexical scope

Answer 2

compare.bind(this) returns a new function. Try this.objects.sort(compare.bind(this));

Answer 3

bind works slightly differently:

const boundCompare = compare.bind(this);
this.sorted = this.objects.sort(boundCompare);