Comments on: NSView with gradient background

By: Berrie

Berrie — Sun, 28 Feb 2010 16:35:18 +0000

You’re right, that’s what you get from migrating at some point. I took it out for clarities sake.

By: Psi

Psi — Sun, 28 Feb 2010 15:17:29 +0000

“the code is based on the new garbage collection mechanism available in Objective-C 2.0, so there are no retain or release calls”

Then what’s that autorelease doing there?

By: Stream

Stream — Fri, 16 Oct 2009 12:40:07 +0000

It would be be useful to have [self setNeedsDisplay:YES], [self displayIfNeeded]; calls within custom setters

By: Berrie

Berrie — Wed, 16 Jul 2008 19:44:42 +0000

Again, well spotted. I’ve corrected the property statement.

By: Demitri

Demitri — Wed, 16 Jul 2008 12:07:50 +0000

Thanks for the code – this is nicely illustrative. One small error in the listing above: the third property statement should say “angle”, not “value”.

Cheers,

Demitri

By: Berrie

Berrie — Thu, 26 Jun 2008 05:56:29 +0000

Well spotted, I’ve changed the example to fix these flaws.

By: Joan Lluch

Joan Lluch — Wed, 25 Jun 2008 21:37:27 +0000

As far as I understand the code has some memory management flaws (even if you are using garbage collection)

[A] – The following line :

startingColor = [NSColor colorWithCalibratedWhite:1.0 alpha:1.0];

can potentially produce a released object access since the NSColor will be autoreleased in the next run loop, so you need to include [startingColor retain] to avoid it, or simply use [self setStartingColor:[NSColor colorWithCalibratedWhite:1.0 alpha:1.0]] ;

The code actually works because you use [myGradientView setStartingColor: ] in your controller, but the above code is still faulty.

[B] – The drawRect method produces a memory leak each time it is called (which may be potentially very often) because aGradient is never released. You must explicitly release it after using it (this is fine if garbage collection is enabled though)

Regards,

Joan

By: Berrie

Berrie — Thu, 10 Jan 2008 05:57:44 +0000

Good point. Makes the code simpler and doesn’t distract from the core message.

I’ve updated the code in the posting.

By: David

David — Thu, 10 Jan 2008 00:22:28 +0000

If you are using objc-c 2.0 then why not use properties? Get rid of the setters and have in interface:
@property(copy) NSColor *startingColor;
@property(copy) NSColor *endingColor;
@property(assign) int angle;

then in implementation section:
@synthesize startingColor, endingColor, angle;

But will be good to see article on using NSGradient with buttons.