(Objective-C) DynamoDB - GetItem

The GetItem operation returns a set of attributes for the item with the given primary key. If there is no matching item, GetItem does not return any data and there will be no Item element in the response.

For more information, see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_GetItem.html

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#import <CkoRest.h>
#import <CkoAuthAws.h>
#import <CkoJsonObject.h>
#import <CkoStringBuilder.h>
#import <NSString.h>

CkoRest *rest = [[CkoRest alloc] init];
BOOL success;

// Implements the following CURL command:

// curl -X POST https://dynamodb.us-west-2.amazonaws.com/ \
//   -H "Accept-Encoding: identity" \
//   -H "Content-Type: application/x-amz-json-1.0" \
//   -H "Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>" \
//   -H "X-Amz-Date: <Date>" \
//   -H "X-Amz-Target: DynamoDB_20120810.GetItem" \
//   -d '{
//     "TableName": "Thread",
//     "Key": {
//         "ForumName": {
//             "S": "Amazon DynamoDB"
//         },
//         "Subject": {
//             "S": "How do I update multiple items?"
//         }
//     },
//     "ProjectionExpression":"LastPostDateTime, Message, Tags",
//     "ConsistentRead": true,
//     "ReturnConsumedCapacity": "TOTAL"
// }'

// Use the following online tool to generate REST code from a CURL command
// Convert a cURL Command to REST Source Code

CkoAuthAws *authAws = [[CkoAuthAws alloc] init];
authAws.AccessKey = @"AWS_ACCESS_KEY";
authAws.SecretKey = @"AWS_SECRET_KEY";
// Don't forget to change the region to your particular region. (Also make the same change in the call to Connect below.)
authAws.Region = @"us-west-2";
authAws.ServiceName = @"dynamodb";
// SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
[rest SetAuthAws: authAws];

// URL: https://dynamodb.us-west-2.amazonaws.com/
BOOL bTls = YES;
int port = 443;
BOOL bAutoReconnect = YES;
success = [rest Connect: @"dynamodb.us-west-2.amazonaws.com" port: [NSNumber numberWithInt: port] tls: bTls autoReconnect: bAutoReconnect];
if (success != YES) {
    NSLog(@"%@%d",@"ConnectFailReason: ",[rest.ConnectFailReason intValue]);
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// Note: The above code does not need to be repeatedly called for each REST request.
// The rest object can be setup once, and then many requests can be sent.  Chilkat will automatically
// reconnect within a FullRequest* method as needed.  It is only the very first connection that is explicitly
// made via the Connect method.

// Use this online tool to generate code from sample JSON:
// Generate Code to Create JSON

// The following JSON is sent in the request body.

// {
//   "TableName": "Thread",
//   "Key": {
//     "ForumName": {
//       "S": "Amazon DynamoDB"
//     },
//     "Subject": {
//       "S": "How do I update multiple items?"
//     }
//   },
//   "ProjectionExpression": "LastPostDateTime, Message, Tags",
//   "ConsistentRead": true,
//   "ReturnConsumedCapacity": "TOTAL"
// }

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"TableName" value: @"Thread"];
[json UpdateString: @"Key.ForumName.S" value: @"Amazon DynamoDB"];
[json UpdateString: @"Key.Subject.S" value: @"How do I update multiple items?"];
[json UpdateString: @"ProjectionExpression" value: @"LastPostDateTime, Message, Tags"];
[json UpdateBool: @"ConsistentRead" value: YES];
[json UpdateString: @"ReturnConsumedCapacity" value: @"TOTAL"];

[rest AddHeader: @"Content-Type" value: @"application/x-amz-json-1.0"];
[rest AddHeader: @"X-Amz-Target" value: @"DynamoDB_20120810.GetItem"];
[rest AddHeader: @"Accept-Encoding" value: @"identity"];

CkoStringBuilder *sbRequestBody = [[CkoStringBuilder alloc] init];
[json EmitSb: sbRequestBody];
CkoStringBuilder *sbResponseBody = [[CkoStringBuilder alloc] init];
success = [rest FullRequestSb: @"POST" uriPath: @"/" requestBody: sbRequestBody responseBody: sbResponseBody];
if (success != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

int respStatusCode = [rest.ResponseStatusCode intValue];
NSLog(@"%@%d",@"response status code = ",respStatusCode);
if (respStatusCode >= 400) {
    NSLog(@"%@%d",@"Response Status Code = ",respStatusCode);
    NSLog(@"%@",@"Response Header:");
    NSLog(@"%@",rest.ResponseHeader);
    NSLog(@"%@",@"Response Body:");
    NSLog(@"%@",[sbResponseBody GetAsString]);
    return;
}

CkoJsonObject *jsonResponse = [[CkoJsonObject alloc] init];
[jsonResponse LoadSb: sbResponseBody];

jsonResponse.EmitCompact = NO;
NSLog(@"%@",[jsonResponse Emit]);

// Sample JSON response:
// (Sample code for parsing the JSON response is shown below)

// {
//   "ConsumedCapacity": {
//     "CapacityUnits": 1,
//     "TableName": "Thread"
//   },
//   "Item": {
//     "Tags": {
//       "SS": [
//         "Update",
//         "Multiple Items",
//         "HelpMe"
//       ]
//     },
//     "LastPostDateTime": {
//       "S": "201303190436"
//     },
//     "Message": {
//       "S": "I want to update multiple items in a single call. What's the best way to do that?"
//     }
//   }
// }

// Sample code for parsing the JSON response...
// Use the following online tool to generate parsing code from sample JSON:
// Generate Parsing Code from JSON

NSString *strVal = 0;

int ConsumedCapacityCapacityUnits = [[jsonResponse IntOf: @"ConsumedCapacity.CapacityUnits"] intValue];
NSString *ConsumedCapacityTableName = [jsonResponse StringOf: @"ConsumedCapacity.TableName"];
NSString *ItemLastPostDateTimeS = [jsonResponse StringOf: @"Item.LastPostDateTime.S"];
NSString *ItemMessageS = [jsonResponse StringOf: @"Item.Message.S"];
int i = 0;
int count_i = [[jsonResponse SizeOfArray: @"Item.Tags.SS"] intValue];
while (i < count_i) {
    jsonResponse.I = [NSNumber numberWithInt: i];
    strVal = [jsonResponse StringOf: @"Item.Tags.SS[i]"];
    i = i + 1;
}