SKUserData singleton save-on-write dictionary subclass

SKUserData.m

#import <Foundation/Foundation.h>

@interface SKUserData : NSMutableDictionary

+ (id)sharedInstance;

@end




#import "SKUserData.h"

@implementation SKUserData

+ (id)sharedInstance {
    static dispatch_once_t pred = 0;
    __strong static id _sharedObject = nil;
    dispatch_once(&pred, ^{
        _sharedObject = [[self alloc] init];
    });
    return _sharedObject;
}

-(id)init {
    NSString *plistPath = [[NSBundle mainBundle] pathForResource:@"userData" ofType:@"plist"];
    self = [[NSMutableDictionary dictionaryWithContentsOfFile:plistPath] retain];
    NSAssert(self, @"plist doesn't exist");
    return self;
}

- (void)setValue:(NSString*)value forKey:(NSString*)key {
    [super setValue:value forKey:key];
    
    NSString *plistPath = [[NSBundle mainBundle] pathForResource:@"userData" ofType:@"plist"];
    [self writeToFile:plistPath atomically:YES];
}

@end