Category methods to traverse object graph and view tree.

NSObject+RLTraverse.h

#import <Foundation/Foundation.h>


// RLTraverseObjectGraphBlock
typedef void (^RLTraverseObjectGraphBlock)(id obj, NSUInteger depth, NSUInteger idx, id parent, BOOL *stop); // If you want to stop traversing completely, set YES to *stop.

// RLChildrenGetter
typedef id (^RLChildrenGetter)(id obj, NSUInteger depth, NSUInteger idx, id parent); // Return object which responds to enumerateObjetsUsingBlock: method. If you don't want to dive deeper, return nil.

@interface NSObject (RLTraverse)
- (void)traverseObjectGraphUsingBlock:(RLTraverseObjectGraphBlock)block childrenGetter:(RLChildrenGetter)childrenGetter;
@end

NSObject+RLTraverse.m

#import "NSObject+RLTraverse.h"


@implementation NSObject (RLTraverse)

- (BOOL)_traverseObjectGraphUsingBlock:(RLTraverseObjectGraphBlock)block childrenGetter:(RLChildrenGetter)childrenGetter depth:(NSUInteger)depth index:(NSUInteger)index parent:(id)parent
{
    __block BOOL stopped = NO;
    
    // Execute block
    block(self, depth, index, parent, &stopped);
    if (stopped) {
        return YES;
    }
    
    // Enumerate children
    if (childrenGetter) {
        id children;
        children = childrenGetter(self, depth, index, parent);
        if ([children respondsToSelector:@selector(enumerateObjectsUsingBlock:)]) {
            [children enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
                stopped = [obj _traverseObjectGraphUsingBlock:block childrenGetter:childrenGetter depth:(depth + 1) index:idx parent:self];
                if (stopped) {
                    *stop = stopped;
                }
            }];
        }
    }
    
    return stopped;
}

- (void)traverseObjectGraphUsingBlock:(RLTraverseObjectGraphBlock)block childrenGetter:(RLChildrenGetter)childrenGetter
{
    // Call primitive method
    [self _traverseObjectGraphUsingBlock:block childrenGetter:childrenGetter depth:0 index:0 parent:nil];
}

@end

UIView+RLTraverse.h

#import <UIKit/UIKit.h>


// RLTraverseViewTreeBlock
typedef void (^RLTraverseViewTreeBlock)(UIView *view, NSUInteger depth, NSUInteger idx, BOOL *stop);

@interface UIView (RLTraverse)
- (void)traverseViewTreeUsingBlock:(RLTraverseViewTreeBlock)block;
@end

UIView+RLTraverse.m

#import "NSObject+RLTraverse.h"
#import "UIView+RLTraverse.h"


@implementation UIView (RLTraverse)

- (void)traverseViewTreeUsingBlock:(RLTraverseViewTreeBlock)block
{
    // Traverse view tree
    [self
        traverseObjectGraphUsingBlock:^(id obj, NSUInteger depth, NSUInteger idx, id parent, BOOL *stop) {
            block(obj, depth, idx, stop);
        }
        childrenGetter:^(UIView *view, NSUInteger depth, NSUInteger idx, id parent) {
            return view.subviews;
        }
    ];
}

@end