尽管设置TImage :: Picture = NULL不会导致内存泄漏，但是有哪些替代方法可以避免这种混乱呢？

Question

Despite bummi's fine explanation of why Image1.Picture := nil won't cause a memory leak , I'm concerned that it may raise red-flags in the minds of new people reading my code, since its safety is counter-intuitive. Therefore, I'd like to avoid it. What more-intuitive alternatives exist? Although bummi's answer was for Delphi, I'm actually more interested in C++Builder.

Answer 1

The alternative is to use Image->Picture->Assign(NULL); , which is actually what Image->Picture = NULL; does internally.

Answer 2

I've set Image1.Visible to false to cause a picture to disappear.

• Disadvantage: You'll have to restore Visible to true when you want to display the next image.
• Advantage: if you happen to want to display one particular image, but only at certain times, then toggling Visible could be more efficient than clearing and reloading.

Answer 3

If you're worried that the reader doesn't understand what image.Picture := nil; means, and you've established that that is the most straightforward way to clear an image, then add a comment stating what the property setter does.

I don't necessarily agree that it needs any change at all, though. It's well-established that property setters can have side effects, and there is no convention in Delphi that after setting a property to a specific value, that re-reading that property will return that same value. In fact, in the VCL I suspect that properties that don't return the same value that was just set are more common.

Either way, comment or not, I would leave the assignment using nil exactly as it is.

Answer 4

Encapsulating the property assignment provides two advantages:

1. a single location to document the non-leakiness of it ( DRY )
2. a less worrisome-looking interface to use everywhere else

eg:

// Not a memory leak: see http://stackoverflow.com/a/23999207/782738
#define ClearImage(Image) Image->Picture = NULL