delphi Form with multi instance use - delphi

Question

i've an FTP uploader project that uses a form created on run time to start uploading to multiple FTP Servers ( using Indy ) , my issue is as follows ( and i really need your help ) .
On a Form i put an IdFTP Component + an Upload button + public properties named FTPSrvAdrs and SrcFile + TrgFolder like this way :
type
TFtpUploader = class(TForm)
IdFTP: TIdFTP;
StartUpload:TButton;
UploadProgress:TProgressBar;
procedure StartUploadClick(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
FFtpSrvAdrs:String;
FSrcFile:String;
FTargetFtpFld:String;
Procedure StartMyUpload();
procedure SetFtpAdrs(const value:string);
procedure SetSrcFile(const value:string);
procedure SetTargetFtpFld(const value:string);
{ Private declarations }
public
{ Public declarations }
property FtpAdrs:string read FFtpSrvAdrs write SetFtpAdrs;
property SourceFile:string read FSrcFile write SetSrcFile;
property TargetFtpFld:string read FTargetFtpFld write SetTargetFtpFld;
end;
var
FtpUploader: TFtpUploader;
implementation
procedure TFtpUploader.StartUploadClick(Sender: TObject);
begin
StartMyUpload();
end;
procedure TFtpUploader.SetFtpAdrs(const value: string);
begin
FFtpSrvAdrs:=value;
end;
procedure TFtpUploader.SetSrcFile(const value: string);
begin
FSrcFile:=value;
end;
procedure TFtpUploader.SetTargetFtpFld(const value: string);
begin
FTargetFtpFld:=value;
end;
procedure TFtpUploader.StartMyUpload;
var
FtpUpStream: TFileStream;
begin
ftpUpStream:= TFileStream.create(FSrcFile, fmopenread)
try
with IdFTP do begin
Host:= FFtpSrvAdrs;
Username:='MyUserName';
Password:='MyPassword';
end;
IdFTP.Connect(true, 1200)
IdFTP.Passive:= true;
IdFTP.ChangeDir(FTargetFtpFld)
IdFTP.Put(ftpUpStream,FSrcFile, false);
finally
ftpUpStream.Free;
end;
end;
procedure TFtpUploader.FormClose(Sender: TObject; var Action: TCloseAction);
begin
Action:=caFree;
end;
This Form will be created on RunTime ( 4 times = 4 buttons will launch it separately like this way :
in the main form i've this procedure :
Procedure MainForm.UploadTo(FTPSrv,SrcFile,FtpTargetFld:String);
var
FUploadFrm:TFtpUploader;
begin
FUploadFrm:=TFtpUploader.Create(nil);
if assigned(FUploadFrm) then
begin
FUploadFrm.FtpAdrs:=FTPSrv;
FUploadFrm.SourceFile:=SrcFile;
FUploadFrm.TargetFtpFld:=FtpTargetFld;
FUploadFrm.Show;
end;
end;
procedure MainForm.Button1Click(Sender: TObject);
begin
UploadTo('MyFtpSrv_1','MySrcFile_1','MyFtpTargetFld_1');
end;
procedure MainForm.Button2Click(Sender: TObject);
begin
UploadTo('MyFtpSrv_2','MySrcFile_2','MyFtpTargetFld_2');
end;
// same with other 2 buttons
the FtpUploader form is Created / Opened ( 4 instances ) ,The ISSUE IS when i click on StartUpload button the FTP upload process is not started on all these 4 instances , but i've to wait each upload process is done ( finished ) and the other will auto-start , that means not all upload processes are started in same time .
Thank you .

Answer 1

It seems you have to either change Indy library for some non-blocking in-background library (event based or completion port based), or to make your program multi-threading (with it's own bunch of problems like user clicking a button 20 times or closing the form while the process is going, or even closing the program on the run).
Based on http://otl.17slon.com/book/doku.php?id=book:highlevel:async it can look anything like this:
TFtpUploader = class(TForm)
private
CanCloseNow: boolean;
...
procedure TFtpUploader.FormClose(Sender: TObject; var Action: TCloseAction);
begin
if Self.CanCloseNow
then Action := caFree
else Action := caIgnore;
end;
procedure TFtpUploader.MyUploadComplete;
begin
Self.CanCloseNow := True;
Self.Close;
end;
procedure TFtpUploader.StartMyUpload;
begin
Self.CanCloseNow := false;
Self.Enabled := False;
Self.Visible := True;
Application.ProcessMessages;
Parallel.Async(
procedure
var
FtpUpStream: TFileStream;
begin
ftpUpStream:= TFileStream.create(FSrcFile, fmopenread)
try
with IdFTP do begin
Host:= FFtpSrvAdrs;
Username:='MyUserName';
Password:='MyPassword';
Connect(true, 1200)
Passive:= true;
ChangeDir(FTargetFtpFld)
// this does not return until uploaded
// thus would not give Delphi a chance to process buttons
// pressed on other forms.
Put(ftpUpStream,FSrcFile, false);
end;
finally
ftpUpStream.Free;
end;
end
,
Parallel.TaskConfig.OnTerminated(
procedure (const task: IOmniTaskControl)
begin
MyUploadComplete;
end;
);
end;
Or you can use simplier AsyncCalls library http://andy.jgknet.de/blog/bugfix-units/asynccalls-29-asynchronous-function-calls/