5.8 Assembly and connections

Imports: values (has, validate, the Holo*Error classes, the pure helpers) from @holostep-configurators/runtime-client, types from @holostep-configurators/runtime-client/contract, /math and /testing names from those entries; boot from the runtime module the root's loadRuntimeAtFloor resolves to. A type your page defines is your app's: declare it there, never import it from the package.

import type { Connection, DeepReadonly, IModelNode, SceneModel, Session } from '@holostep-configurators/runtime-client/contract';
declare const session: Session;
declare const signal: AbortSignal;
declare const assetBaseUrl: string;
declare const element: IModelNode;                                  // the new element, with its nodeId
declare const anchorId: string;                                     // the element it attaches to
declare function withElement(model: DeepReadonly<SceneModel>, element: IModelNode): SceneModel;
declare function price(connections: readonly Connection[]): void;
const r = await session.transaction(async (tx) => {
  const model = tx.getSceneModel();
  if (!model) throw new Error('no model yet');                         // null before the first model: guard, never `!`
  await tx.setSceneModel(withElement(model, element), { assetBaseUrl });   // staged and loaded, hidden
  const a = await tx.assembly.attach(element.nodeId, { from: 'mp-left', to: { node: anchorId, connector: 'mp-right' } });
  if (!a.attached) throw new Error(a.reason);                          // 'occupied', 'rejected', …; everything rolls back
  return tx.assembly.connections();
}, { undo: 'Add element', expectRevision: session.revision, origin: 'golf-ui' });
if (r.outcome === 'committed') price(r.value);                         // the union narrows: no `!`

5.8 Assembly and connections ​