App backend development

Backend code is the portion of an app that:

• Runs on a computer with a copy of an iModel
• Has access to the local file system
• Can use native libraries

A backend package can be a service, an agent, or an app-specific backend.

• See the app architecture overview for how iTwin.js apps are structured.
• See iModel contents for guidance on whether a data type belongs in the iModel or should be stored in a separate repository.
• See best practices for writing backend code.

App backends require the @itwin/core-backend npm package. The common packages will also be required. Please also note the supported platforms.

These packages provide the following functions to support backend operations:

• Administration

  • IModelHost
  • Initialize Logging

• IModelDb

  • Open an IModelDb
  • Synchronizing with iModelHub
  • Concurrency Control — locks and multi-user editing
  • Writing to an IModelDb
  • EditTxn transaction model and migration guidance
  • iModel Transformation and Data Exchange
  • Optimize iModel with SQLite commands
  • Fonts

• Text Annotations

  • Quantity formatting for text annotation fields

• Working with Schemas and Elements in TypeScript

  • Working with Schemas and Elements in TypeScript
  • Data upgrade callbacks when importing Schemas

• Loading and Creating Elements, ElementAspects, and Models

  • Access Elements
  • Create Elements
  • Delete Elements in Bulk
  • Access ElementAspects
  • Create ElementAspects
  • Access Models
  • Create Models

• ECSQL

  • What is ECSQL?
  • Choosing and executing ECSQL query readers
  • Asynchronous query examples
  • Synchronous query examples
  • Migrating backend query code
  • Frequently used ECSQL queries

• Dealing with Codes

  • Reserve Codes

• Change Summary

  • Change Summary Overview
  • ChangesetReader — low-level changeset reading API

• Workspaces and Settings

  • Workspaces and Settings overview
  • Settings
  • Workspace resources

For services and app backends:

• Exposing the operations of the backend as RpcInterfaces
  • Define one or more RpcInterfaces.
  • Implement the RpcInterfaces.
  • Configure the RpcInterfaces.
  • Serve the RpcInterfaces to clients.