iOS根据输入的时间获取当天是星期几

直接上代码：

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSLog(@"this day is %@", [self getTheDayOfTheWeekByDateString:@"2015-12-18"]);

    // Do any additional setup after loading the view, typically from a nib
    
}
///根据用户输入的时间(dateString)确定当天是星期几,输入的时间格式 yyyy-MM-dd ,如 2015-12-18
-(NSString *)getTheDayOfTheWeekByDateString:(NSString *)dateString{
    
    NSDateFormatter *inputFormatter=[[NSDateFormatter alloc]init];
    
    [inputFormatter setDateFormat:@"yyyy-MM-dd"];
    
    NSDate *formatterDate=[inputFormatter dateFromString:dateString];
    
    NSDateFormatter *outputFormatter=[[NSDateFormatter alloc]init];
    
    [outputFormatter setDateFormat:@"EEEE-MMMM-d"];
    
    NSString *outputDateStr=[outputFormatter stringFromDate:formatterDate];
    
    NSArray *weekArray=[outputDateStr componentsSeparatedByString:@"-"];
    
    return [weekArray objectAtIndex:0];
}