我有一个简单的类,具有以下接口实现。
注意:TPolyBase
是抽象类,TPolyResult
是array of double
;看到他们的代码并不重要,在这里也无关紧要。
//INTERFACE
type
TPolynomialList = class
strict private
FPolynomialList: TObjectList<TPolyBase>;
FResult: TList<TPolyResult>;
FCanGet: boolean;
function GetResult: TList<TPolyResult>;
procedure DoSolve;
public
constructor Create(PolynomialList: TObjectList<TPolyBase>);
destructor Destroy; override;
procedure SolvePolynomials(CompletionHandler: TProc);
property Solutions: TList<TPolyResult> read GetResult;
end;
//IMPLEMENTATION
constructor TPolynomialList.Create(PolynomialList: TObjectList<TPolyBase>);
begin
FPolynomialList := PolynomialList;
FResult := TList<TPolyResult>.Create;
FCanGet := false;
end;
destructor TPolynomialList.Destroy;
begin
FResult.Free;
inherited;
end;
procedure TPolynomialList.DoSolve;
var
i: integer;
begin
for i := 0 to FPolynomialList.Count - 1 do
FResult.Add(FPolynomialList[i].GetSolutions);
FCanGet := true;
end;
function TPolynomialList.GetResult: TList<TPolyResult>;
begin
if FCanGet = false then
raise TEquationError.Create('You must solve the equation first!');
Result := FResult;
end;
procedure TPolynomialList.SolvePolynomials(CompletionHandler: TProc);
begin
TTask.Run(procedure
var
ex: TObject;
begin
try
DoSolve;
TThread.Synchronize(nil, procedure
begin
CompletionHandler;
end);
except
on E: Exception do
begin
ex := AcquireExceptionObject;
TThread.Synchronize(nil, procedure
begin
Writeln( (ex as Exception).Message );
end);
end;
end;
end);
end;
该类将一个对象列表作为输入,并且它具有一个内部重要字段FResult
,该字段将结果提供给用户。只有方法SolvePolynomials完成工作后,才能从吸气剂访问它。
问题出在SolvePolynomials
中。我显示的代码使用了一个任务,因为对象列表的大小可能很大,并且我不想冻结UI。为什么我总是在任务代码中遇到访问冲突?
请注意,以下代码可以正常工作,但这不是我想要的,因为如果我输入15000,程序将冻结几秒钟。
procedure TPolynomialList.SolvePolynomials(CompletionHandler: TProc);
begin
DoSolve;
CompletionHandler;
end;
可能是FPolynomialList
变量吗?如果您查看我的课程,那么“从外面拿走”的唯一内容就是TObjectList<TPolyBase>
,因为在构造函数中,我只是简单地引用了该引用(我希望避免复制ok 15k项)。所有其他变量都没有共享。
我在许多读过的书中都看到了“ Delphi High Performance”之类的书,它很好地执行了一个调用内部“ slow”方法的任务,但在这种情况下,可能会有那些引用弄乱了某些东西。任何想法?
这是我用作测试的代码:
var
a: TObjectList<TPolyBase>;
i, j: integer;
f: TPolynomialList;
s: string;
function GetRandom: integer;
begin
Result := (Random(10) + 1);
end;
begin
a := TObjectList<TPolyBase>.Create(true);
try
for i := 0 to 15000 do
begin
a.Add({*Descendant of TPolyBase*})
end;
f := TPolynomialList.Create(a);
try
f.SolvePolynomials(procedure
var
i, j: integer;
begin
for i := 0 to f.Solutions.Count - 1 do
begin
for j := Low(f.Solutions[i]) to High(f.Solutions[i]) do
Writeln({output the results...})
end;
end);
finally
f.Free;
end;
finally
a.Free;
end;
end.
答案 0 :(得分:5)
您的SolvePolynomials
方法将解决方案委托给另一个线程,并在该线程完成其任务之前返回。在该任务线程正在运行时,有必要对其进行操作的所有数据仍处于活动状态。但是,在您的代码中,您将在SolvePolynomials
退出后立即释放必要的对象实例-在您的任务仍在运行时,因此会出现错误。
您必须将这些对象的释放移至完成处理程序中。
基本上,简化的代码如下:
type
TPolynomialList = class
public
destructor Destroy; override;
procedure DoSolve;
procedure SolvePolynomials(CompletionHandler: TProc);
end;
destructor TPolynomialList.Destroy;
begin
Writeln('Destroyed');
inherited;
end;
procedure TPolynomialList.DoSolve;
begin
Writeln('Solving');
end;
procedure TPolynomialList.SolvePolynomials(CompletionHandler: TProc);
begin
TTask.Run(
procedure
begin
try
DoSolve;
TThread.Synchronize(nil,
procedure
begin
CompletionHandler;
end);
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
end);
end;
procedure Test;
var
f: TPolynomialList;
begin
f := TPolynomialList.Create;
try
f.SolvePolynomials(
procedure
begin
Writeln('Solved');
end);
finally
f.Free;
end;
end;
如果运行它,输出将是:
Destroyed
Solving
Solved
但是,如果将释放变量移至完成处理程序中,则执行顺序将是正确的。
procedure Test;
var
f: TPolynomialList;
begin
f := TPolynomialList.Create;
f.SolvePolynomials(
procedure
begin
Writeln('Solved');
f.Free;
end);
end;
Solving
Solved
Destroyed
对于您的代码,这意味着将a.Free
和f.Free
都移到完成处理程序中。