memory-adapter

A library that implements the Write Model and Read Model Adapter interface for storing events and projections in memory. Useful for development and testing but not for production, obviously 😛.

Methods

build

build({ entityName }, { eventStore, projectionStore )

builds a read-model and write-model adapter

Parameters

| attribute | type | description | | :--- | :--- | :--- | | entityName | string | the name of the entity | | eventStore | object | (optional) an object where keys are entityNames and values are arrays of commit objects | | projectionStore | object | (optional) an object where keys are entity names and values are projections objects keyed by id |

Returns

an object with write model methods and read model methods

Example

const memoryAdapterBuilder = require('serverless-cqrs.memory-adapter')
module.exports = memoryAdapterBuilder.build({ 
  entityName: 'todo'
})

You can also provide the initial eventStore and/or projectionStore objects (both are optional). This is useful when writing tests.

const { test } = require('tap')
const { build } = require('serverless-cqrs.memory-adapter')

test('loadEvents', async assert => {
  const eventStore = {
    'foo': [
      { entityId: '123', version: 0, events: [ 'a' ] },
      { entityId: '123', version: 1, events: [ 'b', 'c' ]},
      { entityId: '123', version: 3, events: [ 'd', 'e', 'f' ] },
      { entityId: '123', version: 6, events: [ 'g', 'h', 'i' ] },
    ]
  }
  const expected = [ 'd', 'e', 'f', 'g', 'h', 'i' ]

  const adapter = build({ entityName: 'foo' }, { eventStore })
  
  const res = await adapter.loadEvents('123', 1)

  assert.deepEquals(res, expected, 'returns events after given version')
})

test('get', async assert => {
  const projectionStore = {
    foo: {
      '123':{
        id: '123',
        version: 0,
        state: 'foobar',
      }
    }
  }

  const expected = {
    id: '123',
    version: 0,
    state: 'foobar',
  }

  const adapter = build({ entityName: 'foo' }, { projectionStore })
 
  const res = await adapter.get('123')

  assert.deepEquals(res, expected, 'returns exisiting projection from store')
})