順序を保存するNSMutableDictionary NSMutableDictionaryなどを継承するのが結構大変なのでNSMutableDictionaryとキーを保持するNSMutableArrayを内包したものを自作。 自分が使うメンバーしか実装していない。

MSOrderdDictionary.h

#import <Foundation/Foundation.h>


@interface MSOrderdDictionary : NSObject <NSCoding>
{
    NSMutableDictionary *dictionary;
    NSMutableArray *array;
}

+ (id)dictionary;
+ (id)dictionaryWithCapacity:(NSUInteger)numItems;

- (id)initWithDictionary:(MSOrderdDictionary *)srcDictionary copyItems:(BOOL)flag;

- (NSUInteger)count;
- (id)objectForKey:(id)aKey;
- (NSEnumerator *)keyEnumerator;

- (void)setObject:(id)anObject forKey:(id)aKey;
- (void)removeObjectForKey:(id)aKey;
- (void)removeAllObjects;

- (NSArray *)allValues;

@end

MSOrderdDictionary.m

#import "MSOrderdDictionary.h"

@implementation MSOrderdDictionary


+ (id)dictionary
{
    return [MSOrderdDictionary dictionaryWithCapacity:10];
}

+ (id)dictionaryWithCapacity:(NSUInteger)numItems
{
    return [[MSOrderdDictionary alloc] initWithCapacity:numItems];
}

- (id)initWithDictionary:(MSOrderdDictionary *)srcDictionary copyItems:(BOOL)flag
{
    self = [super init];

    if (flag) {
        self->dictionary = [NSMutableDictionary dictionaryWithDictionary:srcDictionary->dictionary];
        self->array = [NSMutableArray arrayWithArray:srcDictionary->array];
    }
    else {
        self->dictionary = srcDictionary->dictionary;
        self->array = srcDictionary->array;
    }
    
    return self;
}


- (id)initWithCapacity:(NSUInteger)numItems
{
    self = [super init];
    
    self->dictionary = [[NSMutableDictionary alloc] initWithCapacity:numItems];
    self->array = [[NSMutableArray alloc] initWithCapacity:numItems];
    
    return self;
}

- (void)encodeWithCoder:(NSCoder *)encoder
{
    [encoder encodeObject:dictionary forKey:@"MSOrderdDictionary_dictionary"];
    [encoder encodeObject:array forKey:@"MSOrderdDictionary_array"];
}

- (id)initWithCoder:(NSCoder *)decoder
{
    self = [super init];
    
    self->dictionary = [decoder decodeObjectForKey:@"MSOrderdDictionary_dictionary"];
    self->array = [decoder decodeObjectForKey:@"MSOrderdDictionary_array"];
        
    return self;
}

- (NSUInteger)count
{
    return [dictionary count];
}

- (id)objectForKey:(id)aKey
{
    return [dictionary objectForKey:aKey];
}


- (NSEnumerator *)keyEnumerator
{
    return [dictionary keyEnumerator];
}

- (NSEnumerator *)enumerator
{
    return [dictionary keyEnumerator];
}


- (void)setObject:(id)anObject forKey:(id)aKey
{
    [dictionary setObject:anObject forKey:aKey];
    if (![array containsObject:aKey]) {
        [array addObject:aKey];
    }
}

- (void)removeObjectForKey:(id)aKey
{
    [array removeObject:aKey];
    [dictionary removeObjectForKey:aKey];
}

- (void)removeAllObjects
{
    [dictionary removeAllObjects];
    [array removeAllObjects];
}

- (NSArray *)allValues
{
    return [dictionary objectsForKeys:array notFoundMarker:[NSNull null]];
}


@end

nice