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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, AuthAws, Rest, JsonObject, StringBuilder;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rest: HCkRest;
success: Boolean;
authAws: HCkAuthAws;
bTls: Boolean;
port: Integer;
bAutoReconnect: Boolean;
json: HCkJsonObject;
sbRequestBody: HCkStringBuilder;
sbResponseBody: HCkStringBuilder;
respStatusCode: Integer;
jsonResponse: HCkJsonObject;
strVal: PWideChar;
AttributesLastPostedByS: PWideChar;
AttributesForumNameS: PWideChar;
AttributesLastPostDateTimeS: PWideChar;
AttributesSubjectS: PWideChar;
AttributesMessageS: PWideChar;
i: Integer;
count_i: Integer;

begin
rest := CkRest_Create();

// 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 := CkAuthAws_Create();
CkAuthAws_putAccessKey(authAws,'AWS_ACCESS_KEY');
CkAuthAws_putSecretKey(authAws,'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.)
CkAuthAws_putRegion(authAws,'us-west-2');
CkAuthAws_putServiceName(authAws,'dynamodb');
// SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
CkRest_SetAuthAws(rest,authAws);

// URL: https://dynamodb.us-west-2.amazonaws.com/
bTls := True;
port := 443;
bAutoReconnect := True;
success := CkRest_Connect(rest,'dynamodb.us-west-2.amazonaws.com',port,bTls,bAutoReconnect);
if (success <> True) then
  begin
    Memo1.Lines.Add('ConnectFailReason: ' + IntToStr(CkRest_getConnectFailReason(rest)));
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    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 := CkJsonObject_Create();
CkJsonObject_UpdateString(json,'TableName','Thread');
CkJsonObject_UpdateString(json,'Key.ForumName.S','Amazon DynamoDB');
CkJsonObject_UpdateString(json,'Key.Subject.S','How do I update multiple items?');
CkJsonObject_UpdateString(json,'ConditionExpression','attribute_not_exists(Replies)');
CkJsonObject_UpdateString(json,'ReturnValues','ALL_OLD');

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

sbRequestBody := CkStringBuilder_Create();
CkJsonObject_EmitSb(json,sbRequestBody);
sbResponseBody := CkStringBuilder_Create();
success := CkRest_FullRequestSb(rest,'POST','/',sbRequestBody,sbResponseBody);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;
respStatusCode := CkRest_getResponseStatusCode(rest);
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(CkRest__responseHeader(rest));
    Memo1.Lines.Add('Response Body:');
    Memo1.Lines.Add(CkStringBuilder__getAsString(sbResponseBody));
    Exit;
  end;

jsonResponse := CkJsonObject_Create();
CkJsonObject_LoadSb(jsonResponse,sbResponseBody);

CkJsonObject_putEmitCompact(jsonResponse,False);
Memo1.Lines.Add(CkJsonObject__emit(jsonResponse));

// 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 := CkJsonObject__stringOf(jsonResponse,'Attributes.LastPostedBy.S');
AttributesForumNameS := CkJsonObject__stringOf(jsonResponse,'Attributes.ForumName.S');
AttributesLastPostDateTimeS := CkJsonObject__stringOf(jsonResponse,'Attributes.LastPostDateTime.S');
AttributesSubjectS := CkJsonObject__stringOf(jsonResponse,'Attributes.Subject.S');
AttributesMessageS := CkJsonObject__stringOf(jsonResponse,'Attributes.Message.S');
i := 0;
count_i := CkJsonObject_SizeOfArray(jsonResponse,'Attributes.Tags.SS');
while i < count_i do
  begin
    CkJsonObject_putI(jsonResponse,i);
    strVal := CkJsonObject__stringOf(jsonResponse,'Attributes.Tags.SS[i]');
    i := i + 1;
  end;

CkRest_Dispose(rest);
CkAuthAws_Dispose(authAws);
CkJsonObject_Dispose(json);
CkStringBuilder_Dispose(sbRequestBody);
CkStringBuilder_Dispose(sbResponseBody);
CkJsonObject_Dispose(jsonResponse);

end;