📦 Progress to request of the stream, with options to cancel progress #244
Description
📝 Description:
It would be very useful to enhance TRESTRequest (or provide an extension) to support progress tracking for stream-based requests (especially downloads), with an optional cancel mechanism.
🚀 Motivation
When handling large file downloads (or uploads), providing real-time feedback to the user is important for usability. Additionally, the ability to cancel a long-running request is essential in modern applications, especially when dealing with limited bandwidth or mobile users.
✅ Expected Features
- Event or callback for progress reporting during
Streamdownloads or uploads
(e.g.,OnProgress,OnDownloadProgress) - Ability to cancel the request gracefully from within the event
(e.g., via aCancelflag or method) - Optional integration with
TTask,TThread, or another async approach to ensure non-blocking UI
💡 Simple example Use Case (Delphi)
uses
Winapi.Windows,
System.Classes, System.SysUtils, System.Threading,
Vcl.Forms, Vcl.Dialogs,
RESTRequest4D;
var
CancelDownload: Boolean = False;
procedure DownloadWithProgress(const URL, FileName: string);
var
FileStream: TFileStream;
TotalSize: Int64;
LastReported: TDateTime;
begin
TTask.Run(procedure
var
HTTP: IResponse;
Downloaded: Int64;
begin
try
FileStream := TFileStream.Create(FileName, fmCreate);
try
Downloaded := 0;
LastReported := Now;
HTTP := TRequest.New
.BaseURL(URL)
.Accept('application/octet-stream')
.StreamResponse(FileStream)
.OnReceiveProgress(
procedure(ATotal, ACurrent: Int64; var AAbort: Boolean)
var
Percent: Double;
begin
if ATotal > 0 then
Percent := (ACurrent / ATotal) * 100
else
Percent := 0;
// Update UI (simplified example)
if SecondsBetween(LastReported, Now) >= 1 then
begin
TThread.Synchronize(nil,
procedure
begin
Application.ProcessMessages;
OutputDebugString(PChar(Format('Progress: %.2f%%', [Percent])));
end);
LastReported := Now;
end;
AAbort := CancelDownload;
end)
.Get;
if HTTP.StatusCode = 200 then
ShowMessage('Download completed!')
else
ShowMessage('Download error: ' + HTTP.StatusText);
finally
FileStream.Free;
end;
except
on E: Exception do
TThread.Synchronize(nil,
procedure
begin
ShowMessage('Error: ' + E.Message);
end);
end;
end);
end;
procedure TForm1.btnDownloadClick(Sender: TObject);
const
GitHubAssetURL = 'https://github.com/your-username/your-repo/releases/download/v1.0.0/yourfile.exe';
begin
CancelDownload := False;
DownloadWithProgress(GitHubAssetURL, 'C:\Temp\yourfile.exe');
end;
procedure TForm1.btnCancelarClick(Sender: TObject);
begin
CancelDownload := True;
end;