ArcGIS for JS API (2) get the ID set of element services

Catalog

0. Premise

1. resolvent

2. Sample image

3. Core extension

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0. Premise

        use PotalItem Access to various services , about FeatureLayer, Need to carry out search, Buffer analysis ; If we do general element service operations , Each element service contains FeatureLayer The quantity is also different , therefore , Need to get... Dynamically ;

1. resolvent

// First of all get PotalItem library , And then operate 
var item = PortalItem({
    id: arcgisFeatureLayerID,
});

// Unlike FeatureLayer.when() Get... Like that , For those that are not sure to load , have access to .load(),item.load() It's also Promise asynchronous 
item.load().then(function () {
    var serviceUrl = item.url + "?f=pjson"; //  See the picture below 
    layerIDs = getJSON(serviceUrl);
    //  Traversal read FeatureLayer aggregate 
    var featureLayers = [];
    for (let i=0; i<layerIDs.length; i++){
        featureLayers.push(
            new FeatureLayer({
                portalItem: {id: arcgisFeatureLayerID},
                outFields: ["*"],
                layerId: layerIDs[i]
            });
        );
    }
    //  If you want to get FeatureLayer Field set of , Can one by one layer.when() obtain 
    //  It can also be in item.url Back +"/{layerIDs[i]}"+"?f=pjson", use getJSON obtain 
});

//  Get from the service json data 
function getJSON(url){
    var ids;
    $.ajaxSettings.async = false; //$ representative JQuery, Set up synchronization 
    $.getJSON(url, function(data){
        ids = data.layers.map(function(w){
            return w.id;
        });
    });
    $.ajaxSettings.async = true; // Restore asynchrony 
    return ids;
}

2. Sample image

        url：LA_County_Parcels (FeatureServer)  Click on JSON, It can be JSON Resolved

        

3. Core extension

        Promise It's asynchronous , however arcgis js For multiple element layers , General version settings , Asynchronous is not easy to operate , Sometimes you need to synchronize , therefore , May adopt async function ***(){}, In the function await arcgis js Some of Promise Operation function ！await Must be in async- In the function , as follows ：