对于每个创建的TMyRecord中的每个字符串实例,代码看起来大致类似于以下泄漏内存。我认为我必须访问每个记录并以某种方式释放它 - 可以在不填写每个字符串的情况下完成吗?
function TMyForm.RecordFromThing(thing): TMyRecord;
begin
result.StringVal1 = thing.SomeProperty;
result.StringVal2 = thing.SomeOtherProperty;
end;
function TMyForm.RecordsFromItems: TList<TMyRecord>;
begin
result := TList<TMyRecord>.Create;
for thing in things do
begin
result.Add(RecordFromThing(thing));
end;
end;
procedure TMyForm.Button1Click(Sender: TObject);
var Items: TList<TMyRecord;
begin
Items := RecordsFromItems;
try
//Stuff
finally
// What goes here to free those records?
Items.Clear;
Items.Free;
end
end;
根据David的要求,这是从我的应用程序中剪切并粘贴的实际代码。如果我运行Button1Click,则FastMM报告字符串内存泄漏。
type TPremiumPaymentInstruction = record
SupplierID: string;
FirstName: string;
LastName: string;
PolicyNo: string;
CarrierName: string;
PayAmount: string;
DueDate: string;
PayMethod: string;
Comments: string;
Payee: string;
Address: string;
Address2: string;
City: string;
State: string;
Zip: string;
InRe: string;
BankName: string;
BankABA: string;
AccountName: string;
AccountNo: string;
CreditTo: string;
end;
function TPremiumPaymentManager.RecordFromItem(Item: TListItem): TPremiumPaymentInstruction;
var PolicyID: integer;
Instructions: TDataSet;
function FormatNote(PolicyNo, First, Last: string): string;
begin
result := 'Policy# ' + PolicyNo + '; Insured Name: ' + Last + ' ' + First;
end;
begin
FillChar(result, SizeOf(result), 0);
result.SupplierID := Item.Caption;
result.FirstName := Item.SubItems[INSURED_FIRST_NAME_COLUMN];
result.LastName := Item.SubItems[INSURED_LAST_NAME_COLUMN];
result.PolicyNo := Item.SubItems[POLICY_NUMBER_COLUMN];
result.CarrierName := Item.SubItems[CARRIER_NAME_COLUMN];
result.PayAmount := Item.SubItems[ACTUAL_COLUMN];
result.DueDate := Item.SubItems[DATE_DUE_COLUMN];
result.PayMethod := Item.SubItems[PAYMENT_METHOD_COLUMN];
PolicyID := GetSingleValue('SELECT PolicyID FROM PremiumsDue WHERE PremiumID = :PremiumID;', [(Item as TAdvListItem).KeyValue], 0);
Instructions := GetDS('SELECT I.* FROM Policies P INNER JOIN CarrierPaymentInstructions I ON P.CarrierID = I.CarrierID AND P.PaymentInstruction = I.InstructionDescription WHERE P.PolicyID = ?;', [PolicyID]);
try
Instructions.Open;
Instructions.First;
if result.PayMethod = 'Check' then
begin
result.Comments := Item.SubItems[PAYMENT_NOTE_COLUMN];
result.Payee := Instructions.FieldByName('PayTo').AsString;
result.Address := Instructions.FieldByName('Address1').AsString;
result.Address2 := Instructions.FieldByName('Address2').AsString;
result.City := Instructions.FieldByName('City').AsString;
result.State := Instructions.FieldByName('State').AsString;
result.Zip := Instructions.FieldByName('ZipCode').AsString;
result.InRe := FormatNote(result.PolicyNo, result.FirstName, result.LastName);
end
else
begin
result.BankName := Instructions.FieldByName('PayTo').AsString;
result.BankABA := Instructions.FieldByName('ABANumber').AsString;
result.Address2 := Instructions.FieldByName('Address2').AsString;
result.AccountName := Instructions.FieldByName('AccountName').AsString;
result.AccountNo := Instructions.FieldByName('AccountNumber').AsString;
result.CreditTo := FormatNote(result.PolicyNo, result.FirstName, result.LastName);
end;
finally
Instructions.Free;
end;
end;
function TPremiumPaymentManager.RecordsFromItems: TList<TPremiumPaymentInstruction>;
var item: TListItem;
begin
result := TList<TPremiumPaymentInstruction>.Create;
for item in lvPremiums.Items do
begin
if (not (Item as TAdvListItem).Strikeout) and (Item.SubItems[ACTUAL_COLUMN] <> '') then
result.Add( RecordFromItem(item) );
end;
end;
procedure TPremiumPaymentManager.Button1Click(Sender: TObject);
var Items: TList<TPremiumPaymentInstruction>;
begin
Items := RecordsFromItems;
Items.Clear;
Items.Free;
end;
答案 0 :(得分:4)
字符串是托管类型。编译器负责其分配和释放。编译器编写维护引用计数的代码到字符串数据。当引用计数变为零时,将释放内存。
因此,您不需要释放字符串或确实执行任何显式管理。任何这样做的尝试都可能与编译器执行的操作发生冲突。例如,如果对字符串变量执行原始内存访问,则通过调用FillChar
进行查看,然后将绕过引用计数。
你问题中的代码,除了不完整和部分不编译外,基本上都没问题。完成TList<TMyRecord>
之后,只需将其释放即可。编译器将生成代码以释放所有引用。甚至不需要清除它。
List := TList<TMyRecord>.Create;
try
List.Add(...);
// etc.
finally
List.Free;
end;
这就是你所需要的一切。
由于您提出的问题中的代码基本上与此相同,因此我得出结论,泄漏的原因在其他地方。
您知道什么,您的编辑包含对FillChar
的详细调用。用
Result := Default(TPremiumPaymentInstruction);
您始终需要初始化返回值。甚至返回值通常是初始化的托管类型。但不是以你的方式在for循环中进行调用。去搞清楚。无论如何,总是初始化返回值。 Default(T)
是你的朋友。