ios怎么判断日期是周末？

    - (NSString *)calculateWeek:(NSDate *)date{  
        //计算week数  
        NSCalendar * myCalendar = [NSCalendar currentCalendar];  
        myCalendar.timeZone = [NSTimeZone systemTimeZone];  
        NSInteger week = [[myCalendar components:NSWeekdayCalendarUnit fromDate:date] weekday];  
        NSLog(@"week : %zd",week);  
        switch (week) {  
            case 1:  
            {  
                return @"周日";  
            }  
            case 2:  
            {  
                return @"周一";  
            }  
            case 3:  
            {  
                return @"周二";  
            }  
            case 4:  
            {  
                return @"周三";  
            }  
            case 5:  
            {  
                return @"周四";  
            }  
            case 6:  
            {  
                return @"周五";  
            }  
            case 7:  
            {  
                return @"周六";  
            }  
        }  
          
        return @"";  
    }