OC-清空NSUserDefaults的本地数据

//方法一
NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];

//方法二

• (void)resetDefaults {
  NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];
  NSDictionary * dict = [defs dictionaryRepresentation];
  for (id key in dict) {
  [defs removeObjectForKey:key];
  }
  [defs synchronize];
  }