要保持NSMutableDictionary元素的顺序，可以使用OrderDictionary类来替代NSMutableDictionary。OrderDictionary是一个自定义的字典类，可以保持元素的插入顺序。

下面是一个使用OrderDictionary的示例代码：

#import 

@interface OrderDictionary : NSObject

@property (nonatomic, strong) NSMutableArray *keys;
@property (nonatomic, strong) NSMutableArray *values;

- (void)setObject:(id)object forKey:(id)key;
- (id)objectForKey:(id)key;
- (NSArray *)allKeys;
- (NSArray *)allValues;

@end

@implementation OrderDictionary

- (instancetype)init {
    self = [super init];
    if (self) {
        self.keys = [NSMutableArray array];
        self.values = [NSMutableArray array];
    }
    return self;
}

- (void)setObject:(id)object forKey:(id)key {
    if ([self.keys containsObject:key]) {
        NSUInteger index = [self.keys indexOfObject:key];
        [self.values replaceObjectAtIndex:index withObject:object];
    } else {
        [self.keys addObject:key];
        [self.values addObject:object];
    }
}

- (id)objectForKey:(id)key {
    if ([self.keys containsObject:key]) {
        NSUInteger index = [self.keys indexOfObject:key];
        return self.values[index];
    }
    return nil;
}

- (NSArray *)allKeys {
    return [self.keys copy];
}

- (NSArray *)allValues {
    return [self.values copy];
}

@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        OrderDictionary *dictionary = [[OrderDictionary alloc] init];
        
        [dictionary setObject:@"Value 1" forKey:@"Key 1"];
        [dictionary setObject:@"Value 2" forKey:@"Key 2"];
        [dictionary setObject:@"Value 3" forKey:@"Key 3"];
        
        NSArray *keys = [dictionary allKeys];
        NSArray *values = [dictionary allValues];
        
        for (NSUInteger i = 0; i < keys.count; i++) {
            NSLog(@"Key: %@, Value: %@", keys[i], values[i]);
        }
    }
    return 0;
}

在这个示例中，我们创建了一个OrderDictionary类来保持元素的插入顺序。该类内部使用两个可变数组来保存键和值，通过setObject:forKey:方法来设置键值对，通过objectForKey:方法来获取值，通过allKeys和allValues方法来获取所有的键和值。

输出结果为：

Key: Key 1, Value: Value 1
Key: Key 2, Value: Value 2
Key: Key 3, Value: Value 3

可以看到，元素的顺序与插入顺序保持一致。