Simulating iOS memory warnings

MemoryWarnings.m

#if TARGET_IPHONE_SIMULATOR
#import <objc/objc-class.h>

// http://cocoawithlove.com/2008/02/imp-of-current-method.html
IMP impOfCallingMethod(id lookupObject, SEL selector)
{
    NSUInteger returnAddress = (NSUInteger)__builtin_return_address(0);
    NSUInteger closest = 0;
    
    // Iterate over the class and all superclasses
    Class currentClass = object_getClass(lookupObject);
    while (currentClass)
    {
        // Iterate over all instance methods for this class
        unsigned int methodCount;
        Method *methodList = class_copyMethodList(currentClass, &methodCount);
        unsigned int i;
        for (i = 0; i < methodCount; i++)
        {
            // Ignore methods with different selectors
            if (method_getName(methodList[i]) != selector)
            {
                continue;
            }
            
            // If this address is closer, use it instead
            NSUInteger address = (NSUInteger)method_getImplementation(methodList[i]);
            if (address < returnAddress && address > closest)
            {
                closest = address;
            }
        }
		
        free(methodList);
        currentClass = class_getSuperclass(currentClass);
    }
    
    return (IMP)closest;
}

// http://cocoawithlove.com/2008/03/supersequent-implementation.html
#define invokeSupersequent(...) \
([self getImplementationOf:_cmd \
after:impOfCallingMethod(self, _cmd)]) \
(self, _cmd, ##__VA_ARGS__)

#define invokeSupersequentNoParameters() \
([self getImplementationOf:_cmd \
after:impOfCallingMethod(self, _cmd)]) \
(self, _cmd)

@interface NSObject (SupersequentImplementation)
- (IMP)getImplementationOf:(SEL)lookup after:(IMP)skip;
@end

@implementation NSObject (SupersequentImplementation)
// Lookup the next implementation of the given selector after the
// default one. Returns nil if no alternate implementation is found.
- (IMP)getImplementationOf:(SEL)lookup after:(IMP)skip
{
    BOOL found = NO;
    
    Class currentClass = object_getClass(self);
    while (currentClass)
    {
        // Get the list of methods for this class
        unsigned int methodCount;
        Method *methodList = class_copyMethodList(currentClass, &methodCount);
        
        // Iterate over all methods
        unsigned int i;
        for (i = 0; i < methodCount; i++)
        {
            // Look for the selector
            if (method_getName(methodList[i]) != lookup)
            {
                continue;
            }
            
            IMP implementation = method_getImplementation(methodList[i]);
            
            // Check if this is the "skip" implementation
            if (implementation == skip)
            {
                found = YES;
            }
            else if (found)
            {
                // Return the match.
                free(methodList);
                return implementation;
            }
        }
		
        // No match found. Traverse up through super class' methods.
        free(methodList);
		
        currentClass = class_getSuperclass(currentClass);
    }
    return nil;
}
@end

// http://idevrecipes.com/2011/05/04/debugging-magic-auto-simulate-memory-warnings/
@implementation UIViewController (MemoryWarningCategory)
- (void) viewDidAppear:(BOOL)animated {
	IMP superSequentImp = (IMP)[self getImplementationOf:_cmd after:impOfCallingMethod(self, _cmd)];
    ((void(*)(id, SEL, BOOL))superSequentImp)(self, _cmd, animated);

	// If we are running in the simulator then simulate a memory warning.
	NSLog(@"Faking a memory warning");
	CFNotificationCenterPostNotification(CFNotificationCenterGetDarwinNotifyCenter(), (CFStringRef)@"UISimulatedMemoryWarningNotification", NULL, NULL, true);
}
@end 
#endif