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    <p>Here's a simple example how you can do it...</p> <pre><code>const WM_MY_RESULT = WM_USER + $1; type TMyThread = class(TThread) private FKilled: Boolean; FListLock: TRTLCriticalSection; FList: TList; FJobAdded: TEvent; protected procedure Execute; override; procedure DoJob(AJob: Integer); public constructor Create(CreateSuspended: Boolean); destructor Destroy; override; procedure Kill; procedure PushJob(AJob: Integer); function JobCount: Integer; function GetJob: Integer; end; TThreadingForm = class(TForm) lstResults: TListBox; se: TSpinEdit; btn: TButton; procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); procedure btnClick(Sender: TObject); private FThread: TMyThread; procedure OnMyResultMessage(var Msg: TMessage); message WM_MY_RESULT; public { Public declarations } end; var ThreadingForm: TThreadingForm; implementation {$R *.dfm} { TMyThread } constructor TMyThread.Create(CreateSuspended: Boolean); begin FKilled := False; InitializeCriticalSection(FListLock); FList := TList.Create; FJobAdded := TEvent.Create(nil, True, False, 'job.added'); inherited; end; destructor TMyThread.Destroy; begin FList.Free; FJobAdded.Free; DeleteCriticalSection(FListLock); inherited; end; procedure TMyThread.DoJob(AJob: Integer); var res: Integer; begin res := AJob * AJob * AJob * AJob * AJob * AJob; Sleep(1000); // so it would take some time PostMessage(ThreadingForm.Handle, WM_MY_RESULT, res, 0); end; procedure TMyThread.Execute; begin inherited; while not FKilled or not Self.Terminated do begin EnterCriticalSection(FListLock); if JobCount &gt; 0 then begin LeaveCriticalSection(FListLock); DoJob(GetJob) end else begin FJobAdded.ResetEvent; LeaveCriticalSection(FListLock); FJobAdded.WaitFor(10000); end; end; end; function TMyThread.GetJob: Integer; begin EnterCriticalSection(FListLock); try Result := Integer(FList[0]); FList.Delete(0); finally LeaveCriticalSection(FListLock); end; end; function TMyThread.JobCount: Integer; begin EnterCriticalSection(FListLock); Result := FList.Count; LeaveCriticalSection(FListLock); end; procedure TMyThread.Kill; begin FKilled := True; FJobAdded.SetEvent; Terminate; end; procedure TMyThread.PushJob(AJob: Integer); begin EnterCriticalSection(FListLock); try FList.Add(Pointer(AJob)); FJobAdded.SetEvent; finally LeaveCriticalSection(FListLock); end; end; { TThreadingForm } procedure TThreadingForm.OnMyResultMessage(var Msg: TMessage); begin lstResults.Items.Add(IntToStr(Msg.WParam)); end; procedure TThreadingForm.FormCreate(Sender: TObject); begin FThread := TMyThread.Create(False); end; procedure TThreadingForm.FormDestroy(Sender: TObject); begin FThread.Kill; FThread.WaitFor; FThread.Free; end; procedure TThreadingForm.btnClick(Sender: TObject); begin FThread.PushJob(se.Value); end; </code></pre>
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    1. PODelphi thread that waits for data, processes it, then resumes waiting
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    1. USEgon
    1. USEgon
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    1. COYour thread class is coded badly. It will raise an AV when it accesses one of the private object fields in the `Execute` method when they have already been freed in the destructor. To prevent that you need to terminate the thread and `WaitFor` it before you free anything.
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    2. COYeah I agree... I think I really didn't think everything through properly...
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    3. COIMHO calls to Enter/Leave a critical section should be wrapped by a try..finally to avoid leaving the CS locked if an exception occurs.
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