张志敏的技术专栏

import { loadModules } from 'esri-loader';

// 使用 esri-loader 提供的 loadModules 方法加载这两个模块
const [QueryTask, FeatureLayer] = await loadModules<[
    __esri.QueryTaskConstructor,
    __esri.FeatureLayerConstructor
]>([
    'esri/tasks/QueryTask',
    'esri/layers/FeatureLayer'
]);
// 使用 FeatureLayer 服务的地址创建 QueryTask ， 并请求数据
const queryTask: __esri.QueryTask = new QueryTask({
    url: 'https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/Landscape_Trees/FeatureServer/0'
});
const featureSet: __esri.FeatureSet = await queryTask.execute({
    where: '1 = 1',
    outFields: ['*'],
    outSpatialReference: { wkid: 4326 },
    returnGeometry: true
});
// QueryTask 返回的结果是一个 FeatureSet ， 可以很方便的创建 FeatureLayer
const featureLayer: __esri.FeatureLayer = new FeatureLayer({
    geometryType: featureSet.geometryType as any,
    fields: featureSet.fields,
    source: featureSet.features,
    spatialReference: featureSet.spatialReference,
    objectIdField: featureSet.fields.find(f => f.type === 'oid').name
});
// 将 FeatureLayer 添加到地图
view.map.add(featureLayer);

import { loadModules } from 'esri-loader';

// 使用 esri-loader 提供的 loadModules 方法加载 FeatureLayer 模块
const [FeatureLayer] = await loadModules<[
    __esri.FeatureLayerConstructor
]>([
    'esri/layers/FeatureLayer'
]);
// 根据 FeatureLayer 的属性， 构造 json 数据以创建 FeatureLayer ；
const featureLayer: __esri.FeatureLayer = new FeatureLayer({
    fields: [
        { name: 'FID', type: 'oid' },
        { name: 'Tree_ID', type: 'integer' }
    ],
    geometryType: 'point',
    spatialReference: { wkid: 4326 },
    objectIdField: 'FID',
    source: [
        {
            attributes: { 'FID': 1, 'Tree_ID': 102 },
            geometry: { x: -82.44119300239268, y: 35.610448315062335, type: 'point' }
        },
        {
            attributes: { 'FID': 2, 'Tree_ID': 103 },
            geometry: { x: -82.441111192058187, y: 35.6104788975222, type: 'point' }
        }
    ]
});