javascript - Javascript 函数内未定义的 Angular 变量？

Question

我有一个 OpenLayers map 变量，如下所示:

this.map = new Map({
  target: 'map',
  moveTolerance: 2,
  layers: [this.capaFondo, this.capaPropia, this.vector],
  view: new View({
    projection: proyeccion,
    center: fromLonLat([-1.629950, 42.62], proyeccion),
    zoom: 9.3
  })
});

我正在尝试处理这样的单击:

this.map.on('singleclick', function(evt) {
  const p = new Point(evt.coordinate).transform(this.map.getView().getProjection(), proyeccion);
  const properties = ['CP:geometry'];
  const featureRequest = new WFS().writeGetFeature({
        srsName: 'EPSG:25830',
        featurePrefix: 'CP',
        featureTypes: ['CadastralParcel'],
        outputFormat: 'application/json',
        propertyNames: properties,
        filter: containsFilter('geometry', p, 'EPSG:25830')
  });
}

但在函数内部，map 变量似乎未定义。

如何获取其中的map值？任何帮助都会很棒!

Answer 1

函数创建一个新的上下文。为了使其按照您期望的方式工作，您可以将 function (evt) {} 更改为箭头函数，如下所示:

this.map.on('singleclick', (evt) => {
  const p = new Point(evt.coordinate).transform(this.map.getView().getProjection(), proyeccion);
  const properties = ['CP:geometry'];
  const featureRequest = new WFS().writeGetFeature({
        srsName: 'EPSG:25830',
        featurePrefix: 'CP',
        featureTypes: ['CadastralParcel'],
        outputFormat: 'application/json',
        propertyNames: properties,
        filter: containsFilter('geometry', p, 'EPSG:25830')
  });
}

更多关于 this 如何在 JS 中工作的信息，请参阅 this great answer