Advice on "Invalid Pointer Operation" when using complex records
- by Xaz
Env: Delphi 2007
<JustificationI tend to use complex records quite frequently as they offer almost all of the advantages of classes but with much simpler handling.</Justification
Anyhoo, one particularly complex record I have just implemented is trashing memory (later leading to an "Invalid Pointer Operation" error).
This is an example of the memory trashing code:
sSignature := gProfiles.Profile[_stPrimary].Signature.Formatted(True);
On the second time i call it i get "Invalid Pointer Operation"
It works OK if i call it like this:
AProfile := gProfiles.Profile[_stPrimary];
ASignature := AProfile.Signature;
sSignature := ASignature.Formatted(True);
Background Code:
gProfiles: TProfiles;
TProfiles = Record
private
FPrimaryProfileID: Integer;
FCachedProfile: TProfile;
...
public
< much code removed >
property Profile[ProfileType: TProfileType]: TProfile Read GetProfile;
end;
function TProfiles.GetProfile(ProfileType: TProfileType): TProfile;
begin
case ProfileType of
_stPrimary : Result := ProfileByID(FPrimaryProfileID);
...
end;
end;
function TProfiles.ProfileByID(iID: Integer): TProfile;
begin
<snip>
if LoadProfileOfID(iID, FCachedProfile) then
begin
Result := FCachedProfile;
end
else
...
end;
TProfile = Record
private
...
public
...
Signature: TSignature;
...
end;
TSignature = Record
private
public
PlainTextFormat : string;
HTMLFormat : string;
// The text to insert into a message when using this profile
function Formatted(bHTML: boolean): string;
end;
function TSignature.Formatted(bHTML: boolean): string;
begin
if bHTML then
result := HTMLFormat
else
result := PlainTextFormat;
< SNIP MUCH CODE >
end;
OK, so I have a record within a record within a record, which is approaching Inception level confusion and I'm the first to admit is not really a good model. Clearly i am going to have to restructure it. What I would like from you gurus is a better understanding of why it is trashing the memory (something to do with the string object that is created then freed...) so that i can avoid making these kinds of errors in future.
Thanks
