Autodesk Forge: Viewer Extension cant use .getExternalIdMapping()

Question

class IBSProgressExtension extends Autodesk.Viewing.Extension{
    constructor(viewer, options) {
        super(viewer, options);
    }
    load() {
        //For proof of concept project, I will simply store the externalIds here in a variable.
        const allExternalIds = [
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-0006879a',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-000688ee',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068961',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068963',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068a78',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068a0d',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068a0f',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068a11',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068a13',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068c2f',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068c31',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068c33',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b2e',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b30',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b32',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b34',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b3e',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b36',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b38',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b3a',
            '8a00f4c7-0709-4749-88b6-abb0ddccf965-00068b3c'
        ];

        this.viewer.model.getExternalIdMapping(data => onSuccessMapping(data));

        function onSuccessMapping(data) {
            const resArray = [];
            allExternalIds.forEach(externalId => {
                if (data[externalId]) resArray.push(data[externalId], externalId);
            });
            console.log(resArray);
        };

        console.log('IBSProgressExtension is loaded.');
        return true;
    }
};


Autodesk.Viewing.theExtensionManager.registerExtension("IBSProgressExtension", IBSProgressExtension);

Please have a look at my extension and please help me figure out why is this happening. Every time i run it, the devtools logs: ViewerExtension.js:31 Uncaught TypeError: Cannot read properties of undefined (reading 'getExternalIdMapping').

Answer 1

The extensions get loaded before the model so the getExternalIdMapping() method does not have the model properties yet. To handle this scenario, we usually recommend using the viewer events such as Autodesk.Viewing.GEOMETRY_LOADED_EVENT to “catch” the moment when the model is available. It’s better to wait for the event. This will be fired when the model/drawing finishes loading.

Instead of:

this.viewer.model.getExternalIdMapping(data => onSuccessMapping(data));

Try this:

        this.viewer.addEventListener(Autodesk.Viewing.GEOMETRY_LOADED_EVENT, (x) => {
            this.viewer.model.getExternalIdMapping(data => onSuccessMapping(data));
        });