常用存储位置

 NSDictionary *dict = [NSBundle mainBundle].infoDictionary;

    NSString *key = @"CFBundleVersion";
    NSString *lastVersion = [[NSUserDefaults standardUserDefaults] objectForKey:key];
    NSLog(@"%@", lastVersion);
// 将当前版本存到沙盒[[NSUserDefaults standardUserDefaults] setObject:currentVersion forKey:key];

     [[NSUserDefaults standardUserDefaults] synchronize];  // 配合这个同步一下

[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]