Delphi：使用 RTTI 从 TMemo.Text 设置对象属性的非确定性访问冲突

Delphi: non-deterministic access violation using RTTI to set object properties from TMemo.Text

我正在构建一个非常粗糙的 GUI 来建模映射器，它基本上遍历表单上的所有 TEdit 和 TMemo 字段，提取文本并将该文本设置在数据模型对象中。 (解决方案取决于我承认的脆弱的”约定优于配置”方法，仅匹配数据模型中与表单中的字段具有相同名称的属性。)

免责声明：对于臃肿的代码示例感到抱歉。这里是：

表格。

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{ Standard interface section above this line }
type
TfrmMain = class(TForm)
StringField1: TEdit;
StringField2: TMemo;
{ Other fields and procedures dropped for brevity }
private
procedure FillGUIFields();
end;

数据模型。

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TDataModel = class(TObject)
private
FStringField1: string;
FStringField2: string;
{ Getters and setters dropped for brevity }
public
property StringField1: string read GetFStringField1 write SetFStringField1;
property StringField2: string read GetFStringField2 write SetFStringField2;
end;

实现。

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const
MAX_RUNS = 100;

procedure GUIToData(var AObject: TObject; const Form: TForm);
var
c: TRTTIContext;
t: TRTTIType;
prop: TRTTIProperty;
Component: TComponent;
Text: string;
i: integer;
begin
c := TRTTIContext.Create();
t := c.GetType(AObject.ClassType);
for prop in t.GetProperties do begin
Component := Form.FindComponent(prop.Name); // Naive”conv. over conf.” matching
if (Component <> nil) then begin
if (Component is TEdit) then prop.SetValue(AObject, TValue.FromVariant(TEdit (Component).Text));
if (Component is TMemo) then prop.SetValue(AObject, TValue.FromVariant(TMemo(Component).Text));
end;
end;
c.Free();
end;

procedure TfrmMain.btnFetchToModelClick(Sender: TObject);
var
Data: TDataModel;
i: integer;
NumberOfExceptions: integer;
begin
NumberOfExceptions := 0;
for i := 0 to MAX_RUNS – 1 do begin
try
FillGUIFields();
Data := TDataModel.Create();
GUIToData(TObject(Data), self);
Data.Free();
except on E: EAccessViolation do
begin
Inc(NumberOfExceptions);
end;
end;
end;
MessageDlg(‘Number of runs: ‘ + IntToStr(MAX_RUNS) + #13#10 +
‘Number of exceptions: ‘ + IntToStr(NumberOfExceptions), mtInformation, [mbOk], 0);
end;

function TDataModel.GetFStringField1: string;
begin
Result := FStringField1;
end;

procedure TDataModel.SetFStringField1(Value: string);
begin
FStringField1 := Value;
end;

{ Identical getter/setter for StringField2 }

procedure TfrmMain.FillGUIFields;
var
i: integer;
TempBuffer: string;
begin
TempBuffer := ”;
Randomize();
for i := 0 to Random(16) – 1 do begin
if Random(2) = 0 then
TempBuffer := TempBuffer + Chr(Random(25) + 65)
else
TempBuffer := TempBuffer + Chr(Random(25) + 97);
end;
StringField1.Text := TempBuffer; // Filling the edit field
{ Identical code for filling the memo field }
end;

end.

当我运行它时，在大约 27% 的情况下我会遇到访问冲突异常。如果我只设置与 TEdit 字段名称匹配的属性(即 StringField1)，则不会发生异常。如果我直接访问字段(让 getter/setter 直接指向字段或在 GUIToData 过程中使用 t.GetFields)，则不会引发访问冲突。

人们能够复制这个吗？有谁知道是什么导致了这种奇怪的行为？谢谢！

Delphi: non-deterministic access violation using RTTI to set object properties from TMemo.Text

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