Lazy Loading of Blob Fields

WEB TMS WEB Core
1

I'm not sure I have this set up correctly.


I have a TXDataWebDataSet and it's linked to my XData connection and a TXDataWebClient (also linked to the same connection. The data is loaded using:

procedure TMyForm.SetPageId(Value: Integer);
  procedure OnSuccess(Response: TXDataClientResponse);
  begin
    PageDataset.SetJsonData(Response.Result);
    PageDataset.Open;
  end;
begin
  FPageId := Value;
  PageClient.Get(PageDataset.EntitySetName, '$expand=ARTICLE', Value, @OnSuccess);
end;

and then

procedure TMyForm.PageDatasetAfterOpen(DataSet: TDataSet);
var s: String;
begin
  s := PageDatasetARTICLE.Value;
 ContentData.Text := s;
end;

ContentData is a RichEdit control. The standard data comes back ok, but the Article (which is a LazyLoaded blob field doesn't.

Is there a way to do a Get from teh dataset instead of using the TXDataWebClient?

Thanks

2

$expand clause doesn't affect blob fields, only associations. For blob fields you will have to perform an extra GET to get blob content.

Here is an example:



procedure TForm1.WebButton1Click(Sender: TObject);
var
  xhr: TJSXmlHttpRequest;


  procedure _Load;
  begin
    WebMemo1.Lines.Text := xhr.responseText;
  end;


begin
  xhr := TJSXMLHttpRequest.new;
  xhr.open('GET',
    XDataWebConnection1.URL + '/' +
    string(TJSObject(XDataWebDataset1.CurrentData)['ARTICLE@xdata.proxy'])
  );
  xhr.overrideMimeType('text/plain; charset=utf-16');
  xhr.addEventListener('load', @_Load);
  xhr.send;
end;
3

Thanks. 


If the text is edited then is it ok to set the Dataset field with the value and just post the dataset?

BTW a TWebDBRichEdit would be nice :-)
4

Note that with the code above the text is not in Dataset. You are not editing the dataset field.

It's better to also perform a separate PUT request to the same address, with the new content.
5

Are there an examples fo using TJSXMLHttpRequest? One for each (PUT, DELETE, POST) would be nice. Thanks