Headless (no viewer) frontend examples

[r-veenstra]

I'm using Cesium along with the Mesh Export API to visualise an iModel, rather than the default iTwin viewer.

I would still like to use iTwin.js and ECSQL to query my iModel's metadata in various ways.

Are there any examples that demonstrate a headless way to authenticate and connect with an iModel from a frontend application for this purpose? Most samples I can find are either based on the viewer or backend services.

EDIT: Another follow up question - if I already have an Authorization (bearer) token that hasn't expired, is there a way for me to set this somewhere directly so I don't need to implement the full auth process with redirects etc?

I'm just trying to experiment within some very simple vanilla typescript code.

[aruniverse]

Hi Ryan,

Great question; excited to see what you build.

You will first need to initialize IModelApp and since its a headless app I recommend using NoRenderApp. iTwin.js uses RPC for its communication, so you will need to establish a connection via BentleyCloudRpcManager and use the IModelReadRpcInterface. To connect to an iModel from a headless frontend application, you will need to establish an IModelConnection; for your use case you will likely want a CheckpointConnection

Re auth:
iTwin.js-core requires you to just satisfy the requirement of having an AuthorizationClient, which just expects you to return an access token/string (which can be a regular bearer token or a share key). So as along as you have an existing token thats valid you don't need to go through the entire auth flow with sign-ins and redirects, etc.

Here's a some sample code you can use for reference:

const iTwinId = 'YOUR_ITWIN_ID';
const iModelId = 'YOUR_IMODEL_ID';
const rpcInterfaces = [IModelReadRpcInterface];

await NoRenderApp.startup({
  authorizationClient: {
    getAccessToken: async () =>
      'Bearer abc...def',
  },
  rpcInterfaces,
  hubAccess: new FrontendIModelsAccess(),
});

const cloudRpcParams: BentleyCloudRpcParams = {
  info: { title: 'imodel/rpc', version: '' },
  uriPrefix: 'https://api.bentley.com',
};
BentleyCloudRpcManager.initializeClient(cloudRpcParams, rpcInterfaces);

const iModelConn = await CheckpointConnection.openRemote(iTwinId, iModelId);