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];  
}