ARC and NSNib: How to release top-level objects?
ARC and NSNib: How to release top-level objects?
- Subject: ARC and NSNib: How to release top-level objects?
- From: Charles Srstka <email@hidden>
- Date: Fri, 18 Nov 2011 15:47:26 -0600
Okay, I know you’re supposed to use the likes of NSWindowController and NSViewController to load nibs, since they will automatically take care of releasing the top-level objects. However, for the sake of curiosity, I created a new project with ARC just to see what would happen with NSNib. The project contains a xib file named “Foo.xib” whose owner is Foo, and which contains a top-level custom object of class Bar. The implementations of Foo and Bar are as below:
@implementation Foo
- (id)init {
if(self = [super init]) {
NSLog(@"Foo init");
NSNib *nib = [[NSNib alloc] initWithNibNamed:@"Foo" bundle:nil];
NSArray *tlo = nil;
[nib instantiateNibWithOwner:self topLevelObjects:&tlo];
NSLog(@"top-level objects are: %@", tlo);
}
return self;
}
- (void)dealloc {
NSLog(@"Foo dealloc");
}
@end
@implementation Bar
- (id)init {
if(self = [super init]) {
NSLog(@"Bar init");
}
return self;
}
- (void)dealloc {
NSLog(@"Bar dealloc");
}
@end
The application delegate simply contains buttons to create and destroy (by assigning its ivar to nil) a Foo object. Clicking on both, the output looks like this:
2011-11-18 15:42:42.069 test[47843:707] Foo init
2011-11-18 15:42:42.075 test[47843:707] Bar init
2011-11-18 15:42:42.075 test[47843:707] top-level objects are: (
"<Bar: 0x100534800>",
"<NSApplication: 0x1001353f0>"
)
2011-11-18 15:42:47.437 test[47843:707] Foo dealloc
Notice that Bar never gets dealloced.
How is one supposed to manage this? You can easily get the array of the top-level objects, but since ARC doesn’t let you send -release to them, it doesn’t help much. The only ways I can think of to avoid leaking are to do silly things like performSelector:NSSelectorFromString(@“release”) or to wrap the NSNib-using code in a non-ARC source file. Neither seems ideal.
What’s the best way to deal with something like this?
Charles_______________________________________________
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