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copied!<p>Calling <code>Free</code> on a null reference is always safe. Go look in the implementation of <code>TObject.Free</code> to see why.</p> <p>This code is an example of a <em>factory function</em>. Its job is to create a new instance of a class, but if it fails, it needs to make sure it doesn't leak a half-created instance when it throws an exception, so it calls <code>Free</code>. When it's sure it's going to succeed, it transfers ownership of the result to the caller. It still calls <code>Free</code>, but if it's already transfered ownership, then it ends up calling <code>Free</code> on a null reference, and there's no harm done. This code is what transfers ownership:</p> <pre><code>Result := Connection; Connection := nil; </code></pre> <p>The way <em>I</em> would write a factory function would do away with the separate <code>Connection</code> variable. I'd construct the result directly in <code>Result</code>, but free it if there were an exception, like this:</p> <pre><code>function TDBXConnectionFactory.GetConnection(const DBXContext: TDBXContext; const ConnectionProperties: TDBXProperties): TDBXConnection; var ConnectionBuilder: TDBXConnectionBuilder; DelegatePath: TDBXDelegateItem; Connection: TDBXConnection; CombinedProperties: TDBXProperties; begin //... ConnectionBuilder := TDBXConnectionBuilder.Create; try //..lots of setting ConnectionBuilder properties ConnectionBuilder.FInputPassword := CombinedProperties[TDBXPropertyNames.Password]; Result := ConnectionBuilder.CreateConnection; try Result.Open; except Result.Free; raise; end; finally ConnectionBuilder.Free; end; end; </code></pre> <p>That has the same effect.</p>

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