command-handler.md

id	title
command-handler	Command Handler

:::info TypeScript Support

Command handlers are grouped into an Aggregate container object that has an associated TypeScript type:

• Type Name - Aggregate
• Package - @resolve-js/core

:::

A command handler function has the following structure:

(state, command, context) => {
  ...
  return {
    type: 'CommandTypeName',
    payload: { ... },
  }
}

A command handler implementation receives the following arguments:

Argument Name	Description
state	The state object built by the aggregate projection.
command	An object that contains the incoming command's data.
context	An object that contains data and functions related to the current operation.

Context

The context argument is an object with the following fields:

Field Name	Description
jwt	The JSON Web Token attached to the request.
aggregateVersion	The aggregate version that is a number incremented for each subsequent event with the current aggregateId.
encrypt	The user-defined encrypt function.
decrypt	The user-defined decrypt function.

This object can also contain additional fields added by middleware.