[yunqa.de] Re: TDISQLite3Statement memory leak?
- From: Delphi Inspiration <delphi@xxxxxxxx>
- To: yunqa@xxxxxxxxxxxxx
- Date: Mon, 07 Jul 2008 09:59:06 +0200
Clyde England:
>Yes, as per my oroiginal post I already did this. Please see my comment that
>reads "Interestingly if I substitute stmt.close with stmt.free I don't get the
>memory leak, but I have never seen any examples that explicitly call the free
>method like this and am concerned this may cause other issues"
You do not see a call to TDISQLite3UniDirStatement.Free in the demos because
they use TDISQLite3UniDirStatement dropped on a form. This means that Delphi
automatically creates and destroys its instances during application start-up
and shut-down. This supersedes calls to Create and Free.
>So can you please elaborate on:
>
>1. Are there any known issues with using the free method rather than close
There are no known issues with TDISQLite3UniDirStatement.Free. Like with other
Delphi objects, Free is the recommended method to dispose of the object and
release its memory.
>2. Everthing I have in these lists seems to refer to the close method, so
>shouldn't that be the correct way to finalyze things and clean up memory?
No. Each call to TDISQLite3Database.Prepare[16] returns a new instance of
TDISQLite3UniDirStatement which must consequently be freed. Failing to do so
results in a memory leak, which you experienced in your code.
TDISQLite3UniDirStatement.Close = TDataSet.Close
Quote from the Delphi help: "Call Close to set the Active property of a dataset
to false. When Active is false, the dataset is closed; it cannot read or write
data and data-aware controls can?t use it to fetch data or post edits."
TDISQLite3UniDirStatement.Free = TObject.Free
Delphi help: "Use Free to destroy an object. Free automatically calls the
destructor if the object reference is not nil. Any object instantiated at
runtime that does not have an owner should be destroyed by a call to Free so
that it can be properly disposed of and its memory released."
As implemented in TDISQLite3UniDirStatement, Free automatically calls Close, so
you are save to call just Free.
Ralf
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