# Read Model

## Types

### projection

The read model's cache of an entity's state

| attribute | type      | description                                       |
| --------- | --------- | ------------------------------------------------- |
| `id`      | `string`  | ID of the entity                                  |
| `version` | `integer` | Version number of the projection                  |
| `state`   | `object`  | An arbitrary object containing the entity's state |

## Methods

### get

`get(id)`

Retrieve the stored projection for a given entity.

#### Parameters

| attribute | type     | description                     |
| --------- | -------- | ------------------------------- |
| `id`      | `string` | (required) the ID of the entity |

####  Returns

`projection`

### set

`set(id, { version, state })`

Set the  projection state for a given entity.

#### Parameters

| attribute | type      | description                                                |
| --------- | --------- | ---------------------------------------------------------- |
| `id`      | `string`  | (required) the ID of the entity                            |
| `version` | `integer` | (required) the version of the projection                   |
| `state`   | `object`  | (required) an arbitrary object containing the entity state |

####  Returns

`null` 

### batchGet

`batchGet([ ...ids ])`

Fetch multiple projections at once

#### Parameters

| attribute | type    | description                             |
| --------- | ------- | --------------------------------------- |
| `ids`     | `array` | (required) the IDs of entities to fetch |

#### Returns

`[ projections ]` (array of projections) - the projections (if they exist)

### batchWrite

`batchWrite({ id: { version, state }, id: { version, state }, ... })`

Set multiple projections at once

#### Parameters

| attribute | type      | description                                                |
| --------- | --------- | ---------------------------------------------------------- |
| `id`      | `string`  | (required) the ID of the entity                            |
| `version` | `integer` | (required) the version of the projection                   |
| `state`   | `object`  | (required) an arbitrary object containing the entity state |

### search

`search(params)`

Search for projections

#### Parameters

| attribute | type     | description                                     |
| --------- | -------- | ----------------------------------------------- |
| `id`      | `object` | (required) an arbitrary object of search params |

#### Returns

`{ total, data }`

| attribute | type    | description                                  |
| --------- | ------- | -------------------------------------------- |
| `total`   | integer | (required) the total number of records found |
| `data`    | `array` | (required) an array of projection objects    |


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