evalphobia/aws-sdk-go-wrapper

package dynamodb

import (
    SDK "github.com/aws/aws-sdk-go/service/dynamodb"
    "github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
)

// BatchGet executes batch_get_item operation
func (t *Table) BatchGet(req BatchGetRequest) (*BatchGetResponse, error) {
    res, err := t.service.client.BatchGetItem(req.ToInput(t.nameWithPrefix))
    if err != nil {
        return nil, err
    }
    return newBatchGetResponse(res, t.nameWithPrefix), nil
}

type BatchGetRequest struct {
    RequestItems           KeysAndAttributes
    ReturnConsumedCapacity string
}

func (r *BatchGetRequest) ToInput(tableName string) *SDK.BatchGetItemInput {
    i := SDK.BatchGetItemInput{}
    i.RequestItems = make(map[string]*SDK.KeysAndAttributes)
    i.RequestItems[tableName] = r.RequestItems.ToSDK()
    if r.ReturnConsumedCapacity != "" {
        i.ReturnConsumedCapacity = &r.ReturnConsumedCapacity
    }
    return &i
}

type BatchGetResponse struct {
    Responses        []map[string]*SDK.AttributeValue
    UnprocessedKeys  KeysAndAttributes
    ConsumedCapacity []ConsumedCapacity
}

func newBatchGetResponse(output *SDK.BatchGetItemOutput, tableName string) *BatchGetResponse {
    r := &BatchGetResponse{}
    if output == nil {
        return r
    }
    if res, ok := output.Responses[tableName]; ok {
        r.Responses = res
    }
    if keys, ok := output.UnprocessedKeys[tableName]; ok {
        r.UnprocessedKeys = newKeysAndAttributes(keys)
    }
    r.ConsumedCapacity = newConsumedCapacities(output.ConsumedCapacity)
    return r
}

func (r BatchGetResponse) Unmarshal(v interface{}) error {
    return r.UnmarshalWithTagName(v, defaultResultTag)
}

// UnmarshalWithTagName unmarshals given slice pointer sturct and tag name from DynamoDB item result to mapping.
func (r BatchGetResponse) UnmarshalWithTagName(v interface{}, structTag string) error {
    decoder := dynamodbattribute.NewDecoder()
    decoder.TagKey = structTag

    items := make([]*SDK.AttributeValue, len(r.Responses))
    for i, m := range r.Responses {
        items[i] = &SDK.AttributeValue{M: m}
    }
    val := &SDK.AttributeValue{
        L: items,
    }
    if err := decoder.Decode(val, v); err != nil {
        return err
    }
    return nil
}