AGNContainerWalker - class for traversing an Array or Dictionary and broadcasting notifications with the results.

AGNContainerWalker.h

//
//  AGNContainerWalker.h
//  Agnitio iPlanner
//
//  Created by Matt Gough on 14/02/2013.
//  Copyright (c) 2013 Agnitio. All rights reserved.
//

#import <Foundation/Foundation.h>

@class AGNContainerWalker;

@protocol AGNContainerWalkerDelegate <NSObject>
@optional
- (BOOL)containerWalker:(AGNContainerWalker*)walker shouldWalkDictionary:(NSDictionary*)dictionary withKey:(NSString*)key;
- (void)containerWalker:(AGNContainerWalker*)walker willStartDictionary:(NSDictionary*)dictionary withKey:(NSString*)key;
- (void)containerWalker:(AGNContainerWalker*)walker didEndDictionary:(NSDictionary*)dictionary withKey:(NSString*)key;
- (BOOL)containerWalker:(AGNContainerWalker*)walker shouldRewindDictionary:(NSDictionary*)dictionary withKey:(NSString*)key;

- (BOOL)containerWalker:(AGNContainerWalker*)walker shouldWalkArray:(NSArray*)array withKey:(NSString*)key;
- (void)containerWalker:(AGNContainerWalker*)walker willStartArray:(NSArray*)array withKey:(NSString*)key;
- (void)containerWalker:(AGNContainerWalker*)walker didEndArray:(NSArray*)array withKey:(NSString*)key;

- (void)containerWalker:(AGNContainerWalker*)walker didFindNonContainer:(NSObject*)object withKey:(NSString*)key;

@end

@interface AGNContainerWalker : NSObject

- (void)walkContainer:(id)dictOrArray;
- (id)valueForItemAtPathStack:(NSArray*)pathStack;

@property (nonatomic, weak) id<AGNContainerWalkerDelegate> delegate;
@property (nonatomic, readonly) id containerBeingWalked;
@property (nonatomic, readonly) NSArray* pathStack;

@end

AGNContainerWalker.m

//
//  AGNContainerWalker.m
//  Agnitio iPlanner
//
//  Created by Matt Gough on 14/02/2013.
//  Copyright (c) 2013 Agnitio. All rights reserved.
//
#if ! __has_feature(objc_arc)
#warning This file must be compiled with ARC. Use -fobjc-arc flag (or convert project to ARC).
#endif

#import "AGNContainerWalker.h"

@interface AGNContainerWalker()
{
  NSMutableArray* _pathStack;
	id _containerBeingWalked;
	struct {
		unsigned int shouldWalkDictionary:1;
		unsigned int willStartDictionary:1;
		unsigned int didEndDictionary:1;
		unsigned int shouldRewindDictionary:1;
		unsigned int shouldWalkArray:1;
		unsigned int willStartArray:1;
		unsigned int didEndArray:1;
		unsigned int didFindNonContainer:1;
	} _delegateSupports;
}
@end

@implementation AGNContainerWalker

- (id)valueForItemAtPathStack:(NSArray *)pathStack
{
	id result = _containerBeingWalked;
	NSUInteger index = 0;
	NSUInteger count = [pathStack count];
	for (id component in pathStack)
	{
		BOOL isLastItem = index == count - 1 ;
		if ([component isKindOfClass:[NSString class]])
		{ // Its a key in a dictionary
			if (!(isLastItem || [result isKindOfClass:[NSDictionary class]]))
				return nil;
			result = [result objectForKey:component];
		}
		else if ([component isKindOfClass:[NSNumber class]])
		{ // Its an array index
			if (!(isLastItem || [result isKindOfClass:[NSArray class]]))
				return nil;
			result = [result objectAtIndex:[component integerValue]];
		}
		++index;
	}
	
	return result;
}

- (void)walkNonContainer:(id)value withKey:(NSString*)key
{
	if (_delegateSupports.didFindNonContainer)
	{
		if (key)
			[_pathStack addObject:key];
		
		id<AGNContainerWalkerDelegate> delegate = _delegate;
		[delegate containerWalker:self didFindNonContainer:value withKey:key];
		
		if (key)
			[_pathStack removeLastObject];
	}
	
}

- (void)walkDictionary:(NSDictionary*)dictionary withKey:(NSString*)dictKey
{
	id<AGNContainerWalkerDelegate> delegate = _delegate;
	if (_delegateSupports.shouldWalkDictionary)
	{
		if (![delegate containerWalker:self shouldWalkDictionary:dictionary withKey:dictKey])
			return;
	}
	
	if (dictKey)
		[_pathStack addObject:dictKey];
	
	if (_delegateSupports.willStartDictionary)
		[delegate containerWalker:self willStartDictionary:dictionary withKey:dictKey];
	
	for (BOOL keepGoing = YES; keepGoing;)
	{
		//	[dictionary enumerateKeysAndObjectsUsingBlock:^(NSString* key, id value, BOOL* stop) {
		for (NSString*key in dictionary) {
			id value = dictionary[key];
			if ([value isKindOfClass:[NSDictionary class]])
				[self walkDictionary:(NSDictionary*)value withKey:key];
			else if ([value isKindOfClass:[NSArray class]])
				[self walkArray:(NSArray*)value withKey:key];
			else
				[self walkNonContainer:value withKey:key];
		}
		//	];
		
		keepGoing = _delegateSupports.shouldRewindDictionary && [delegate containerWalker:self shouldRewindDictionary:dictionary withKey:dictKey];
	}
	
	if (_delegateSupports.didEndDictionary)
		[delegate containerWalker:self didEndDictionary:dictionary withKey:dictKey];
	
	if (dictKey)
		[_pathStack removeLastObject];
}

- (void)walkArray:(NSArray*)array withKey:(NSString*)arrayKey
{
	id<AGNContainerWalkerDelegate> delegate = _delegate;
	if (_delegateSupports.shouldWalkArray)
	{
		if (![delegate containerWalker:self shouldWalkArray:array withKey:arrayKey])
			return;
	}
	
	if (arrayKey)
		[_pathStack addObject:arrayKey];
	
	if (_delegateSupports.willStartArray)
		[delegate containerWalker:self willStartArray:array withKey:arrayKey];
	
	NSUInteger index = 0;
	for (id value in array)
	{
		[_pathStack addObject:@(index)];
		if ([value isKindOfClass:[NSDictionary class]])
			[self walkDictionary:(NSDictionary*)value withKey:nil];
		else if ([value isKindOfClass:[NSArray class]])
			[self walkArray:(NSArray*)value withKey:nil];
		else
			[self walkNonContainer:value withKey:nil];
		
		++index;
		[_pathStack removeLastObject];
	}
	
	
	if (_delegateSupports.didEndArray)
		[delegate containerWalker:self didEndArray:array withKey:arrayKey];
	
	if (arrayKey)
		[_pathStack removeLastObject];
}

- (void)walkContainer:(id)dictOrArray
{
	_containerBeingWalked = dictOrArray;
	_pathStack = [[NSMutableArray alloc] init];
	
	if ([dictOrArray isKindOfClass:[NSDictionary class]])
		[self walkDictionary:(NSDictionary*)dictOrArray withKey:nil];
	else if ([dictOrArray isKindOfClass:[NSArray class]])
		[self walkArray:(NSArray*)dictOrArray withKey:nil];
	else
	{
		AGNLogLWarning(@"Unexpected object:%@", dictOrArray);
		[self walkNonContainer:dictOrArray withKey:nil];
	}
}

- (void)setDelegate:(id<AGNContainerWalkerDelegate>)delegate
{
	_delegate = delegate;
	
	_delegateSupports.shouldWalkDictionary = [delegate respondsToSelector:@selector(containerWalker:shouldWalkDictionary:withKey:)];
	_delegateSupports.willStartDictionary = [delegate respondsToSelector:@selector(containerWalker:willStartDictionary:withKey:)];
	_delegateSupports.didEndDictionary = [delegate respondsToSelector:@selector(containerWalker:didEndDictionary:withKey:)];
	_delegateSupports.shouldRewindDictionary = [delegate respondsToSelector:@selector(containerWalker:shouldRewindDictionary:withKey:)];
	_delegateSupports.shouldWalkArray = [delegate respondsToSelector:@selector(containerWalker:shouldWalkArray:withKey:)];
	_delegateSupports.willStartArray = [delegate respondsToSelector:@selector(containerWalker:willStartArray:withKey:)];
	_delegateSupports.didEndArray = [delegate respondsToSelector:@selector(containerWalker:didEndArray:withKey:)];
	_delegateSupports.didFindNonContainer = [delegate respondsToSelector:@selector(containerWalker:didFindNonContainer:withKey:)];
}

@end