Objective-C

DynamoDB - Query

See more Amazon DynamoDB Examples

The Query operation finds items based on primary key values. You can query any table or secondary index that has a composite primary key (a partition key and a sort key). Objective-C

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

BOOL success = NO;

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

//  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.Query" \
//    -d '{
//      "TableName": "Reply",
//      "IndexName": "PostedBy-Index",
//      "Limit": 3,
//      "ConsistentRead": true,
//      "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
//      "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
//      "ExpressionAttributeValues": {
//          ":v1": {"S": "Amazon DynamoDB#DynamoDB Thread 1"},
//          ":v2a": {"S": "User A"},
//          ":v2b": {"S": "User C"}
//      },
//      "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": "Reply",
//    "IndexName": "PostedBy-Index",
//    "Limit": 3,
//    "ConsistentRead": true,
//    "ProjectionExpression": "Id, PostedBy, ReplyDateTime",
//    "KeyConditionExpression": "Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b",
//    "ExpressionAttributeValues": {
//      ":v1": {
//        "S": "Amazon DynamoDB#DynamoDB Thread 1"
//      },
//      ":v2a": {
//        "S": "User A"
//      },
//      ":v2b": {
//        "S": "User C"
//      }
//    },
//    "ReturnConsumedCapacity": "TOTAL"
//  }

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"TableName" value: @"Reply"];
[json UpdateString: @"IndexName" value: @"PostedBy-Index"];
[json UpdateInt: @"Limit" value: [NSNumber numberWithInt: 3]];
[json UpdateBool: @"ConsistentRead" value: YES];
[json UpdateString: @"ProjectionExpression" value: @"Id, PostedBy, ReplyDateTime"];
[json UpdateString: @"KeyConditionExpression" value: @"Id = :v1 AND PostedBy BETWEEN :v2a AND :v2b"];
[json UpdateString: @"ExpressionAttributeValues.:v1.S" value: @"Amazon DynamoDB#DynamoDB Thread 1"];
[json UpdateString: @"ExpressionAttributeValues.:v2a.S" value: @"User A"];
[json UpdateString: @"ExpressionAttributeValues.:v2b.S" value: @"User C"];
[json UpdateString: @"ReturnConsumedCapacity" value: @"TOTAL"];

[rest AddHeader: @"Content-Type" value: @"application/x-amz-json-1.0"];
[rest AddHeader: @"X-Amz-Target" value: @"DynamoDB_20120810.Query"];
[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": "Reply"
//    },
//    "Count": 2,
//    "Items": [
//      {
//        "ReplyDateTime": {
//          "S": "2015-02-18T20:27:36.165Z"
//        },
//        "PostedBy": {
//          "S": "User A"
//        },
//        "Id": {
//          "S": "Amazon DynamoDB#DynamoDB Thread 1"
//        }
//      },
//      {
//        "ReplyDateTime": {
//          "S": "2015-02-25T20:27:36.165Z"
//        },
//        "PostedBy": {
//          "S": "User B"
//        },
//        "Id": {
//          "S": "Amazon DynamoDB#DynamoDB Thread 1"
//        }
//      }
//    ],
//    "ScannedCount": 2
//  }

//  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 *ReplyDateTimeS = 0;
NSString *PostedByS = 0;
NSString *IdS = 0;

int ConsumedCapacityCapacityUnits = [[jsonResponse IntOf: @"ConsumedCapacity.CapacityUnits"] intValue];
NSString *ConsumedCapacityTableName = [jsonResponse StringOf: @"ConsumedCapacity.TableName"];
int Count = [[jsonResponse IntOf: @"Count"] intValue];
int ScannedCount = [[jsonResponse IntOf: @"ScannedCount"] intValue];
int i = 0;
int count_i = [[jsonResponse SizeOfArray: @"Items"] intValue];
while (i < count_i) {
    jsonResponse.I = [NSNumber numberWithInt: i];
    ReplyDateTimeS = [jsonResponse StringOf: @"Items[i].ReplyDateTime.S"];
    PostedByS = [jsonResponse StringOf: @"Items[i].PostedBy.S"];
    IdS = [jsonResponse StringOf: @"Items[i].Id.S"];
    i = i + 1;
}