# Multi-Model Requests

## General

### Creation

Multi-model requests are created with the `new`  keyword.

{% hint style="info" %}
You can provide a DynamoDB client instance when creating a new multi model request:`new BatchGetRequest(Person, myDynamoDBClient)` 
{% endhint %}

### Params

Every request instance contains the public `params` property where all params for the request are written to. You might want to use it for debugging purpose but are also able to write on it (eg. non-covered features).

#### Consumed Capacity

You might want to receive the consumed capacity which can be achieved by applying the `returnConsumedCapacity('INDEXES' | 'TOTAL')` method and the usage of `execFullResponse()` instead of `exec()`.

### Execution

All requests provide at least two execution methods:

* `exec()` returns a promise which will resolve to the requested items or void if no items were requested
* `execFullResponse()` returns a promise which will resolve to the full response DynamoDB returns, but `response.Items`  are still mapped for you.

## BatchGet

{% embed url="<https://shiftcode.github.io/dynamo-easy/modules/multi_model_requests_transact_get.html>" %}
technical api doc
{% endembed %}

{% embed url="<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_BatchGetItem.html>" %}
<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API\\_BatchGetItem.html>
{% endembed %}

{% code title="batch-get-request.example.ts" %}

```typescript
import { BatchGetRequest, BatchGetResponse } from '@shiftcoders/dynamo-easy'
import { AnotherModel, Person } from '../models'

const keysToFetch: Array<Partial<Person>> = [{ id: 'vogelsw' }]
const otherKeysToFetch: Array<Partial<AnotherModel>> = [{ propA: 'Foo', propB: 'Bar' }]

new BatchGetRequest()
  .forModel(Person, keysToFetch)
  .forModel(AnotherModel, otherKeysToFetch)
  .exec()
  .then((result: BatchGetResponse) => {
    console.log('items fetched from example table', result.tableNameOfExampleModel)
    console.log('items fetched from another table', result.tableNameOfAnotherModel)
  })
```

{% endcode %}

## BatchWrite

{% embed url="<https://shiftcode.github.io/dynamo-easy/modules/multi_model_requests_batch_write.html>" %}
technical api doc
{% endembed %}

{% embed url="<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_BatchWriteItem.html>" %}
<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API\\_BatchWriteItem.html>
{% endembed %}

{% code title="batch-write-request.example.ts" %}

```typescript
import { BatchWriteRequest } from '@shiftcoders/dynamo-easy'
import { AnotherModel, Person } from '../models'

const keysToDelete: Array<Partial<Person>> = [{ id: 'vogelsw' }]
const otherKeysToDelete: Array<Partial<AnotherModel>> = [{ propA: 'Foo', propB: 'Bar' }]
const objectsToPut: AnotherModel[] = [
  { propA: 'foo', propB: 'bar', updated: new Date() },
  { propA: 'foo2', propB: 'bar2', updated: new Date() },
]

new BatchWriteRequest()
  .returnConsumedCapacity('TOTAL')
  .delete(Person, keysToDelete)
  .delete(AnotherModel, otherKeysToDelete)
  .put(AnotherModel, objectsToPut)
  .execFullResponse()
  .then(resp => {
    console.log(resp.ConsumedCapacity)
  })
```

{% endcode %}

## TransactGet

Execute transactional read operations by providing one or multiple models + keys.

{% embed url="<https://shiftcode.github.io/dynamo-easy/modules/multi_model_requests_transact_get.html>" %}
technical api doc
{% endembed %}

{% embed url="<https://goo.gl/qktiQb>" %}
<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API\\_TransactGetItems.html>
{% endembed %}

{% code title="transact-get-request.example.ts" %}

```typescript
import { TransactGetRequest } from '@shiftcoders/dynamo-easy'
import { AnotherModel, Person } from '../models'

new TransactGetRequest()
  .returnConsumedCapacity('TOTAL')
  .forModel(Person, { id: 'vogelsw' })
  .forModel(AnotherModel, { propA: 'Foo', propB: 'Bar' })
  .exec()
  .then(result => {
    console.log(result[0]) // Person item
    console.log(result[1]) // AnotherModel item
  })
```

{% endcode %}

## TransactWrite

Execute transactional write operations by providing one or multiple transact items (TransactConditionCheck, TransactDelete, TransactPut, TransactUpdate).

{% embed url="<https://goo.gl/8NHwFd>" %}
technical api doc
{% endembed %}

{% embed url="<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_TransactWriteItems.html>" %}
<https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API\\_TransactWriteItems.html>
{% endembed %}

{% code title="transact-write-request.example.ts" %}

```typescript
import {
  attribute,
  TransactConditionCheck,
  TransactDelete,
  TransactPut,
  TransactUpdate,
  TransactWriteRequest,
} from '@shiftcoders/dynamo-easy'
import { AnotherModel, Person } from '../models'

const objectToPut: AnotherModel = { propA: 'Foo', propB: 'Bar', updated: new Date() }

new TransactWriteRequest()
  .transact(
    new TransactConditionCheck(Person, 'vogelsw').onlyIf(attribute('yearOfBirth').gte(1958)),
    new TransactDelete(AnotherModel, 'Foo', 'Bar'),
    new TransactPut(AnotherModel, objectToPut),
    new TransactUpdate(Person, 'vogelsw').updateAttribute('yearOfBirth').set(1984),
  )
  .exec()
  .then(() => console.log('done'))

```

{% endcode %}


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