NSUserDefault

NSUserDefaults * settings = [NSUserDefaults standardUserDefaults] ;
[setttings removeObjectForKey:@"phone"] ;
[setttings setObject:@"123456" forKey:@"phone"] ;
[setttings synchronize] ;

参考资料
http://www.360doc.com/content/15/0714/15/26281448_484856846.shtml
http://blog.csdn.net/lxinl/article/details/11770675
http://www.cnblogs.com/xiaobaizhu/p/3448933.html
https://www.v2ex.com/t/278149