AsyncCalls - Delphi asynchronous function call framework

With AsyncCalls you can execute multiple functions at the same time and synchronize them with an IAsyncCall interface. This allows you to execute time consuming code in a different thread whos result is needed at a later time.

The AsyncCalls.pas unit offers a variety of function prototypes to call asynchronous functions.

Inlined VCL/main thread synchronization is supported. With this you can implement the code that calls a VCL function directly in your thread method without having to use a helper method and TThread.Synchronize. You have full access to all local variables. For Delphi 2009 and newer the TAsyncCalls class utilizes generics and anonymous methods.

Documentation

See DOCUMENTATION.md

Requirements

• Supported compilers: Delphi 5 to 10.1
• Supported platforms: Win32, Win64

Installation

Add the AsyncCalls.pas unit to your project's uses-clause.

Example

Using an anonymous function

procedure TForm1.Button3Click(Sender: TObject); 
var 
  Value: Integer; 
begin 
  TAsyncCalls.Invoke(procedure 
  begin 
    // Executed in a thread
    Value := 10; 
    TAsyncCalls.VCLInvoke(procedure 
    begin 
      ShowMessage('The value may not equal 10: ' + IntToStr(Value)); 
    end); 
    Value := 20; 
    TAsyncCalls.VCLSync(procedure 
    begin 
      ShowMessage('The value equals 20: ' + IntToStr(Value)); 
    end); 
    Value := 30; 
  end); 

  Sleep(1000); 
end; // If the async. function is run yet, the "end" will sync it

Using a global function

function GetFiles(Directory: string; Filenames: TStrings): Integer;
var
  h: THandle;
  FindData: TWin32FindData;
begin
  h := FindFirstFile(PChar(Directory + '\*.*'), FindData);
  if h <> INVALID_HANDLE_VALUE then
  begin
    repeat
      if (StrComp(FindData.cFileName, '.') <> 0) and (StrComp(FindData.cFileName, '..') <> 0) then
      begin
        Filenames.Add(Directory + '\' + FindData.cFileName);
        if FindData.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY <> 0 then
          GetFiles(Filenames[Filenames.Count - 1], Filenames);
      end;
    until not FindNextFile(h, FindData);
    Windows.FindClose(h);
  end;
  Result := 0;
end;

procedure TFormMain.ButtonGetFilesClick(Sender: TObject); 
var
  Dir1, Dir2, Dir3: IAsyncCall;
  Dir1Files, Dir2Files, Dir3Files: TStrings;
begin
  Dir1Files := TStringList.Create;
  Dir2Files := TStringList.Create;
  Dir3Files := TStringList.Create;
  ButtonGetFiles.Enabled := False;
  try
    Dir1 := TAsyncCalls.Invoke<string, TStrings>(GetFiles, 'C:\Windows\System32', Dir1Files);
    Dir2 := TAsyncCalls.Invoke<string, TStrings>(GetFiles, 'D:\Html', Dir2Files);
    Dir3 := TAsyncCalls.Invoke<string, TStrings>(GetFiles, 'E:', Dir3Files);

    { Wait until both async functions have finished their work. While waiting make the UI
	  reacting on user interaction. }
    while AsyncMultiSync([Dir1, Dir2], True, 10) = WAIT_TIMEOUT do
      Application.ProcessMessages;
    Dir3.Sync; // Force the Dir3 function to finish here

    MemoFiles.Lines.Assign(Dir1Files);
    MemoFiles.Lines.AddStrings(Dir2Files);
    MemoFiles.Lines.AddStrings(Dir3Files);
  finally
    ButtonGetFiles.Enabled := True;
    Dir3Files.Free;
    Dir2Files.Free;
    Dir1Files.Free;
  end;
end;