A UIViewController subclass which automagically releases its UIView-derived instance variables upon -dealloc and -viewDidUnload

gistfile1.m

/* Base UIViewController subclass for your iPhone applications which automatically
 * releases your instance variables pointing to UIView objects or UIView-subclassed objects,
 * limiting the work you have to do in -dealloc and -viewDidUnload
 *
 * All you have to do is make your UIViewController subclasses inherit from BaseUIViewController
 * instead of UIViewController
 *
 * The helper function that disposes of objects is generalized and can be used for other
 * types of objects as well.
 *
 * Use this code ONLY if you understand what it does, and have correctly read the comments.
 *
 * Public domain code, (c) 2010 Florent Pillet (florent@florentpillet.com)
 */
 
/* BaseUIViewController.h */
#import <UIKit/UIKit.h>
 
@interface BaseUIViewController : UIViewController
{
}
@end
 
/* BaseUIViewController.m */
#import <objc/runtime.h>
#import "BaseUIViewController.h"
 
@interface BaseUIViewController ()
- (void)releaseOutlets;
@end

// Prototype for the helper function
void ReleaseInstanceVariablesDerivingFrom(Class ivarBaseClass, id object, Class objectBaseClass);

@implementation BaseUIViewController
 
- (void)dealloc
{
	[self releaseOutlets];
	[super dealloc];
}
 
- (void)viewDidUnload
{
	[self releaseOutlets];
	[super viewDidUnload];
}
 
- (void)releaseOutlets
{
	// Release all instance variables that are subclasses of UIView in this object
	// and it objects deriving from ourselves.
	ReleaseInstanceVariablesDerivingFrom([UIView class], self, [UIViewController class]);
}

@end

void ReleaseInstanceVariablesDerivingFrom(Class ivarBaseClass, id object, Class objectBaseClass)
{
	// Release all instance variables of an object that derive from UIView.
	// Only process the instance and parent classes, up to the first "inheritedFrameworkClass"
	// i.e. if you have a UIViewController subclass, you should call this with:
	//
	// ReleaseInstanceVariablesDerivingFrom([UIView class], self, [UIViewController class]);
	// 
	// Note, though, that all ivars which don't derive from the base class (here, UIView)
	// MUST be nil'd before calling this function, otherwise bad things™ will ensue.



	Class objectClass = [object class];
	while (objectClass && objectClass != objectBaseClass)
	{
		unsigned int count = 0;
		Ivar *ivars = class_copyIvarList(objectClass, &count);
		if (ivars != NULL)
		{
			Ivar *ip = ivars;
			for (unsigned int i = 0; i < count; i++, ip++)
			{
				const char *type = ivar_getTypeEncoding(*ip);
				if (type[0] == '@' && type[1] == '"')
				{
					id value = object_getIvar(object, *ip);
					if ([value isKindOfClass:ivarBaseClass])
					{
#ifdef DEBUG
						NSLog(@"-> releasing ivar %s value %p of type %s of class %@, retainCount=%u", ivar_getName(*ip), value, type, [value class], [value retainCount]);
#endif
						[value release];
						object_setIvar(object, *ip, nil);
						break;
					}
				}
			}
			free(ivars);
		}
		objectClass = class_getSuperclass(objectClass);
	}
}