How to pass an array as parameter to a task with SetParameter from OmniThreadLibrary?

Question

In Delphi XE8, I am trying to pass an array to the OTL task in SetParameter from OmniThreadLibrary:

implementation

type
  TCookie = record
    Name:    string;
    Value:   string;
    ExpDate: string;
    ModDate: string;
  end;

  TCookieArray = array of TCookie;

var
  CurCookies: TCookieArray;

procedure TForm1.btnStartTaskClick(Sender: TObject);
begin
  SetLength(CurCookies, 2);
  CurCookies[0].Name  := 'username';
  CurCookies[0].Value := 'Paul';
  CurCookies[1].Name  := 'password';
  CurCookies[1].Value := 'none';

  FGetCookieDetailsTask := CreateTask(GetCookieEntries, 'GetCookieEntries')
    .MonitorWith(OTLMonitor)
    // Compiler complaint:
    .SetParameter('CookiesArray', TOmniValue.FromArray<TCookieArray>(CurCookies))
    .Run;
end;

The compiler complains about the SetParameter line:

[dcc32 Error] Unit1.pas(310): E2010 Incompatible types:
'System.TArray<Unit1.TCookieArray>' and 'TCookieArray'

Unfortunately, there are no examples in the OTL book on how to use FromArray in SetParameter to pass an array to the task.

So how can this be done?

EDIT: ba__friend asked that I show the source code from my solution in the comments of his answer:

  FGetCookieDetailsTask := CreateTask(GetCookieEntries, 'GetCookieEntries')
    .MonitorWith(OTLMonitor)
    // Now no compiler complaint:
    .SetParameter('CookiesArray', CurCookies)
    .Run;

procedure GetCookieEntries(const task: IOmniTask);
var
  TaskCookies, HostCookies: TCookieArray;
begin
  HostCookies := task.Param['CookiesArray'];
  TaskCookies := Copy(HostCookies, 0, Length(HostCookies));

Answer 1

There are two problems in your code.

1) TCookieArray has to be declared as

TCookieArray = TArray<TCookie>;

From the compiler's standpoint, array of T and TArray<T> are (sadly) not the same thing.

2) FromArray<T> expects the type T to be the array item type, not the array type (see OtlCommon), so you have to change it from

TOmniValue.FromArray<TCookieArray>

to

TOmniValue.FromArray<TCookie>

To access this array from a task, call:

var
  cookies: TCookieArray;

cookies := task.Param['CookiesArray'].ToArray<TCookie>;

---

Side note: This is how things should work. In OTL up to (and including) 3.04b, record type is, however, not handled correctly in ToArray<T> and FromArray<T>. A fix for that has just been committed to the GitHub.

If you want to fix your copy manually, two modifications are needed.

In TOmniValue.CastFrom<T>, this block

if ds = 0 then // complicated stuff
  {$IFDEF OTL_ERTTI}

should be changed to

if ds = 0 then // complicated stuff
  if ti^.Kind = tkRecord then
    Result.SetAsRecord(CreateAutoDestroyObject(
      TOmniRecordWrapper<T>.Create(value)))
  else
    {$IFDEF OTL_ERTTI}

In TOmniValue.CastTo<T>, following block

if ds = 0 then // complicated stuff
  {$IFDEF OTL_ERTTI}

should be changed to

if ds = 0 then // complicated stuff
  if ti.Kind = tkRecord then
    Result := TOmniRecordWrapper<T>(CastToRecord.Value).Value
  else
    {$IFDEF OTL_ERTTI}