My solution

Objective-C Programming (2nd Edition) Appendix: The Objective-C Runtime
1

[code]#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import “BNRTower.h”

NSArray *BNRHierarchyForClass(Class cls)
{
// Delcare an array to hold the list of
// this class and all its superclasses, building a hierarchy
NSMutableArray *classHierarchy = [NSMutableArray array];

// Keep climbing the class hierarchy until we get to a class with no
// superclass
for (Class c = cls; c != nil; c = class_getSuperclass(c)) {
    NSString *className = NSStringFromClass(c);
    [classHierarchy insertObject:className atIndex:0];
}

return classHierarchy;

}

NSArray *BNRMethodForClass(Class cls)
{
unsigned int methodCount = 0;

Method *methodList = class_copyMethodList(cls, &methodCount);

NSMutableArray *methodArray = [NSMutableArray array];

for (int m = 0; m < methodCount; m++) {
    // Get the current Method
    Method currentMethod = methodList[m];
    // Get the selector for the current method
    SEL methodSelector = method_getName(currentMethod);
    // Add its string representation to the array
    [methodArray addObject:NSStringFromSelector(methodSelector)];
}

free(methodList);

return methodArray;

}

NSArray *BNRIvarForClass(Class cls)
{
unsigned int ivarCount = 0;

Ivar *ivarList = class_copyIvarList(cls, &ivarCount);

NSMutableArray *ivarArray = [NSMutableArray array];

for (int i = 0; i < ivarCount; i++) {
    Ivar currentIvar = ivarList[i];
    NSString *ivarName = [NSString stringWithUTF8String:ivar_getName(currentIvar)];
    [ivarArray addObject];
}

free(ivarList);

return ivarArray;

}

int main(int argc, const char * argv[])
{

@autoreleasepool {

    // You don't have an object to do the observing, but send
    // the addObserver: message anyway, to kick off the runtime updates
    BNRTower *myTowel = [BNRTower new];
    [myTowel addObserver:nil
              forKeyPath:@"location"
                 options:NSKeyValueObservingOptionNew
                 context:NULL];

    // Create an array of dictionaries, where each dictionary
    // will end up holding the class name, hierarchy, and method list
    // for a given class
    NSMutableArray *runtimeClassesInfo = [NSMutableArray array];
    
    // Declare a variable to hold the number of registered classes
    unsigned int classCount = 0;

    // Get a pointer to a list of all registered classes
    // currently loaded by your application.
    // The number of registered classes is returned by reference
    Class *classList = objc_copyClassList(&classCount);

    // For each class in the list...
    for (int i = 0; i < classCount; i++) {
        // Treat the classList as a C array to get a Class from it
        Class currentClass = classList[i];

        // Get the class's name as a string
        NSString *className = NSStringFromClass(currentClass);

        NSArray *hierarchy = BNRHierarchyForClass(currentClass);

        NSArray *methods = BNRMethodForClass(currentClass);

        NSArray *ivars = BNRIvarForClass(currentClass);

        NSDictionary *classInfoDict = @{ @"classname": className,
                                         @"hierarchy": hierarchy,
                                         @"methods": methods,
                                         @"ivars": ivars };

        [runtimeClassesInfo addObject:classInfoDict];
    }

    // We're done with the class list buffer, so free it
    free(classList);

    // Sort the classes info array alphabetically be classname, and log it.
    NSSortDescriptor *alphaAsc = [NSSortDescriptor sortDescriptorWithKey:@"classname"
                                                               ascending:YES];
    NSArray *sortedArray = [runtimeClassesInfo sortedArrayUsingDescriptors:@[alphaAsc]];

    NSLog(@"There are %ld classes registered with this program's Runtime.",
          sortedArray.count);
    NSLog(@"%@", sortedArray);

}
return 0;

}[/code]