清除NSUserdefault内容

//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];  
}

亲测第一种好用, 第二种没试