持久化存储文件在文件系统中的位置

1. 先获取应用程序文档目录的路径
   1. #pragma mark - PATHS- (NSString *)applicationDocumentsDirectory {    if (debug == 1) {        NSLog(@"Running %@ '%@'",self.class, NSStringFromSelector(_cmd));    }        return [NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES) lastObject];}
2. 返回包含Stores的子目录路径的NSURL，如果没有则创建
   1. - (NSURL *)applicationStoresDirectory {    if (debug == 1) {        NSLog(@"Running %@ '%@'",self.class, NSStringFromSelector(_cmd));    }        NSURL *storesDirectory = [[NSURL fileURLWithPath:[self applicationDocumentsDirectory]] URLByAppendingPathComponent:@"Stores"];        NSFileManager *fileManager = [NSFileManager defaultManager];    if (![fileManager fileExistsAtPath:[storesDirectory path]]) {        NSError *error = nil;        if ([fileManager createDirectoryAtURL:storesDirectory withIntermediateDirectories:YES attributes:nil error:&error]) {            if (debug == 1) {                NSLog(@"Running %@ '%@'",self.class, NSStringFromSelector(_cmd));            }else{                NSLog(@"FAILD to Create Stores directory:%@",error);            }                    }    }        return storesDirectory;}
3. 返回完整路径
   1. - (NSURL *)storeURL {    if (debug == 1) {        NSLog(@"Running %@ '%@'",self.class, NSStringFromSelector(_cmd));    }    return [[self applicationStoresDirectory] URLByAppendingPathComponent:storeFilename];}