JavaScript ArcGIS TopFilter用法及代码示例

AMD: require(["esri/rest/support/TopFilter"], (TopFilter) => { /* code goes here */ });

ESM: import TopFilter from "@arcgis/core/rest/support/TopFilter";

类： esri/rest/support/TopFilter

继承: TopFilter > Accessor

自从：用于 JavaScript 4.20 的 ArcGIS API

此类定义了顶级过滤器参数，用于对 FeatureLayer 中的要素执行顶级要素查询。在函数层上调用任何顶级查询方法时，必须在 TopFeaturesQuery 对象上设置此参数。它用于设置 top 特征查询使用的 groupByFields、orderByFields 和计数条件。例如，您可以使用FeatureLayer的queryTopFeatures()方法查询美国每个州人口最多的三个县。

// query the top three most populous counties from each state.
// Results will be ordered based the population of each county in descending order
// top query will run against all features available in the service
const query = new TopFeaturesQuery({
  outFields: ["State, Pop_total, County"],
  topFilter: new TopFilter({
    topCount: 3,
    groupByFields: ["State"],
    orderByFields: ["Pop_total DESC"]
  })
});
featureLayer.queryTopFeatures(query)
  .then(function(response){
     // returns a feature set with features containing the most populous
     // three counties in each state ordered by the number of population.
     // The following attributes are returned as well: State, Pop_total, County
   });