(Delphi ActiveX) DynamoDB - DeleteItem

Deletes a single item in a table by primary key. You can perform a conditional delete operation that deletes the item if it exists, or if it has an expected attribute value.

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

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rest: TChilkatRest;
success: Integer;
authAws: TChilkatAuthAws;
bTls: Integer;
port: Integer;
bAutoReconnect: Integer;
json: TChilkatJsonObject;
sbRequestBody: TChilkatStringBuilder;
sbResponseBody: TChilkatStringBuilder;
respStatusCode: Integer;
jsonResponse: TChilkatJsonObject;
strVal: WideString;
AttributesLastPostedByS: WideString;
AttributesForumNameS: WideString;
AttributesLastPostDateTimeS: WideString;
AttributesSubjectS: WideString;
AttributesMessageS: WideString;
i: Integer;
count_i: Integer;

begin
rest := TChilkatRest.Create(Self);

// 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.DeleteItem" \
//   -d '{
//     "TableName": "Thread",
//     "Key": {
//         "ForumName": {
//             "S": "Amazon DynamoDB"
//         },
//         "Subject": {
//             "S": "How do I update multiple items?"
//         }
//     },
//     "ConditionExpression": "attribute_not_exists(Replies)",
//     "ReturnValues": "ALL_OLD"
// }'

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

authAws := TChilkatAuthAws.Create(Self);
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.ControlInterface);

// URL: https://dynamodb.us-west-2.amazonaws.com/
bTls := 1;
port := 443;
bAutoReconnect := 1;
success := rest.Connect('dynamodb.us-west-2.amazonaws.com',port,bTls,bAutoReconnect);
if (success <> 1) then
  begin
    Memo1.Lines.Add('ConnectFailReason: ' + IntToStr(rest.ConnectFailReason));
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// 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?"
//     }
//   },
//   "ConditionExpression": "attribute_not_exists(Replies)",
//   "ReturnValues": "ALL_OLD"
// }

json := TChilkatJsonObject.Create(Self);
json.UpdateString('TableName','Thread');
json.UpdateString('Key.ForumName.S','Amazon DynamoDB');
json.UpdateString('Key.Subject.S','How do I update multiple items?');
json.UpdateString('ConditionExpression','attribute_not_exists(Replies)');
json.UpdateString('ReturnValues','ALL_OLD');

rest.AddHeader('Content-Type','application/x-amz-json-1.0');
rest.AddHeader('X-Amz-Target','DynamoDB_20120810.DeleteItem');
rest.AddHeader('Accept-Encoding','identity');

sbRequestBody := TChilkatStringBuilder.Create(Self);
json.EmitSb(sbRequestBody.ControlInterface);
sbResponseBody := TChilkatStringBuilder.Create(Self);
success := rest.FullRequestSb('POST','/',sbRequestBody.ControlInterface,sbResponseBody.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;
respStatusCode := rest.ResponseStatusCode;
Memo1.Lines.Add('response status code = ' + IntToStr(respStatusCode));
if (respStatusCode >= 400) then
  begin
    Memo1.Lines.Add('Response Status Code = ' + IntToStr(respStatusCode));
    Memo1.Lines.Add('Response Header:');
    Memo1.Lines.Add(rest.ResponseHeader);
    Memo1.Lines.Add('Response Body:');
    Memo1.Lines.Add(sbResponseBody.GetAsString());
    Exit;
  end;

jsonResponse := TChilkatJsonObject.Create(Self);
jsonResponse.LoadSb(sbResponseBody.ControlInterface);

jsonResponse.EmitCompact := 0;
Memo1.Lines.Add(jsonResponse.Emit());

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

// {
//   "Attributes": {
//     "LastPostedBy": {
//       "S": "fred@example.com"
//     },
//     "ForumName": {
//       "S": "Amazon DynamoDB"
//     },
//     "LastPostDateTime": {
//       "S": "201303201023"
//     },
//     "Tags": {
//       "SS": [
//         "Update",
//         "Multiple Items",
//         "HelpMe"
//       ]
//     },
//     "Subject": {
//       "S": "How do I update multiple items?"
//     },
//     "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

AttributesLastPostedByS := jsonResponse.StringOf('Attributes.LastPostedBy.S');
AttributesForumNameS := jsonResponse.StringOf('Attributes.ForumName.S');
AttributesLastPostDateTimeS := jsonResponse.StringOf('Attributes.LastPostDateTime.S');
AttributesSubjectS := jsonResponse.StringOf('Attributes.Subject.S');
AttributesMessageS := jsonResponse.StringOf('Attributes.Message.S');
i := 0;
count_i := jsonResponse.SizeOfArray('Attributes.Tags.SS');
while i < count_i do
  begin
    jsonResponse.I := i;
    strVal := jsonResponse.StringOf('Attributes.Tags.SS[i]');
    i := i + 1;
  end;
end;