TMonitor在Delphi-2009中严重损坏.它已在Delphi-XE2 upd 4中起作用，此处的答案是基于(或更新)的.

TMonitor is badly broken in Delphi-2009. It became functional in Delphi-XE2 upd 4, which the answer here is based on (or newer).

这里，对象池基于线程安全的TThreadedQueue.

Here, the object pool is based on a thread-safe TThreadedQueue.

内置创建对象的机制具有线程安全性. 从池中获取对象是线程安全的，并且在创建池时定义了超时. 队列大小也在池创建时定义，其中还传递了用于创建对象的回调例程.

A mechanism for creating pooled objects is built in with thread safety. Getting an object from the pool is thread-safe and a timeout is defined at pool creation. The queue size is also defined at pool creation, where a callback routine for object creation also is passed.

uses
  System.Classes,Generics.Collections,System.SyncObjs,System.Diagnostics;

type
  TObjectConstructor = function : TObject;

  TMyPool = Class
  private
    FQueueSize,FAllocatedObjects : integer;
    FGetTimeOut : Integer;
    FQueue : TThreadedQueue<TObject>;
    FObjectConstructor : TObjectConstructor;
    FCS : TCriticalSection;
    function AllocateNewObject : TObject;
  public
    Constructor Create( AnObjectConstructor : TObjectConstructor;
                        QueueSize           : Integer;
                        GetTimeOut          : Integer);
    Destructor Destroy; override;
    procedure Put( const AnObject : TObject);
    function Get( var AnObject : TObject) : TWaitResult;
  End;

function TMyPool.AllocateNewObject: TObject;
begin
  FCS.Enter;
  Try
    if Assigned(FObjectConstructor) and
       (FAllocatedObjects < FQueueSize)
    then
    begin
      Inc(FAllocatedObjects);
      Result := FObjectConstructor;
    end
    else
      Result := Nil;
  Finally
    FCS.Leave;
  End;
end;

constructor TMyPool.Create( AnObjectConstructor : TObjectConstructor;
                            QueueSize           : Integer;
                            GetTimeOut          : Integer);
begin
  Inherited Create;

  FCS := TCriticalSection.Create;
  FAllocatedObjects := 0;
  FQueueSize := QueueSize;
  FObjectConstructor := AnObjectConstructor;
  FGetTimeOut := GetTimeOut;
  FQueue := TThreadedQueue<TObject>.Create(FQueueSize+1,Infinite,10);
  // Adding an extra position in queue to safely remove all items on destroy
end;

destructor TMyPool.Destroy;
var
  AQueueSize : integer;
  AnObject : TObject;
  wr : TWaitResult;
begin
  FQueue.PushItem(Nil); // Just to make sure we have an item in queue
  repeat // Free objects in queue
    AnObject := nil;
    wr := FQueue.PopItem(AQueueSize,AnObject);
    if (wr = wrSignaled) then
      AnObject.Free;
  until (AQueueSize = 0);
  FQueue.Free;
  FCS.Free;

  Inherited;
end;

function TMyPool.Get(var AnObject: TObject) : TWaitResult;
var
  sw : TStopWatch;
begin
  AnObject := nil;
  // If queue is empty, and not filled with enough objects, create a new.
  sw := TStopWatch.Create;
  repeat
    sw.Start;
    Result := FQueue.PopItem( AnObject); // Timeout = 10 ms
    if (Result = wrTimeOut) and
       (FAllocatedObjects < FQueueSize) and
       Assigned(FObjectConstructor)
    then begin  // See if a new object can be allocated
      AnObject := Self.AllocateNewObject;
      if Assigned(AnObject) then
      begin
        Result := wrSignaled;
        Exit;
      end;
    end;
    sw.Stop;
  until (Result = wrSignaled) or (sw.ElapsedMilliseconds > FGetTimeOut);
end;

procedure TMyPool.Put( const AnObject: TObject);
begin
  FQueue.PushItem(AnObject); // Put object back into queue
end;

像这样定义您的TObjectConstructor函数:

function MyObjectConstructor : TObject;
begin
  Result := TMyObject.Create( {Some optional parameters});
end;

以及使用示例:

var
  AnObject : TObject;
  MyObject : TMyObject;
  wr : TWaitResult;
begin
  wr := MyObjPool.Get(AnObject);
  if (wr = wrSignaled) then 
  begin
    MyObject := TMyObject(AnObject);
    try
      // Do something with MyObject
    finally
      MyObjPool.Put(AnObject);
    end;
  end;
end