我正在开发一个使用Ionic Native Google Maps plugin的Ionic 3应用程序。我尝试使用node pool和Google Maps示例来创建标记池。
我的问题是，在createPool函数的新Promise中，this.map是未定义的，即使它是由loadMap（）函数创建的。我读了这篇关于承诺的文章，但我不知道它如何适用于我的情况。如果有人能帮助我，我将不胜感激。

ngAfterViewInit() {
    this.platform.ready()
      .then(_ => {
        return this.loadMap()
      })
      .then(_ => {
        this.markerpool = this.createPool();
        this.markerpool.on('factoryCreateError', err => console.log(err));
      })
} 

createPool() {
    var factory = {
      create: function () {
        return new Promise((resolve, reject) => {
          this.map.addMarker({
            icon: 'assets/icon/sun.png',
            visible: false
          })
            .then(marker => {
              // icon anchor set to the center of the icon
              marker.setIconAnchor(42, 37);
              resolve(marker);
            })
        })
      },
      destroy: function (marker: Marker) {
        return new Promise((resolve, reject) => {
          marker.remove();
          resolve();
        })
      }
    }
    var opts = {
      max: 60, // maximum size of the pool
      min: 20 // minimum size of the pool
    }
    return GenericPool.createPool(factory, opts);
  }

loadMap() {
    this.mapElement = document.getElementById('map');
    let mapOptions: GoogleMapOptions = {
      camera: {
        target: {
          lat: 40.9221968,
          lng: 14.7907662
        },
        zoom: maxzoom,
        tilt: 30
      },
      preferences: {
        zoom: {
          minZoom: minzoom,
          maxZoom: maxzoom
        }
      }
    };

    this.map = this.googleMaps.create(this.mapElement, mapOptions);
    this.zoomLevel = this.getZoomLevel(maxzoom);
    return this.map.one(GoogleMapsEvent.MAP_READY);
  }