iOS 根据时间戳获取星期几

+ (NSString *)dateWeekWithDateString:(NSString *)dateString
{
    NSTimeInterval time=[dateString doubleValue];
    NSDate *date=[NSDate dateWithTimeIntervalSince1970:time];
    NSCalendar *gregorian = [[NSCalendar alloc]
                             initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    NSDateComponents *weekdayComponents =
    [gregorian components:NSCalendarUnitWeekday fromDate:date];
    NSInteger _weekday = [weekdayComponents weekday];
    NSString *weekStr;
    if (_weekday == 1) {
        weekStr = @"星期日";
    }else if (_weekday == 2){
        weekStr = @"星期一";
    }else if (_weekday == 3){
        weekStr = @"星期二";
    }else if (_weekday == 4){
        weekStr = @"星期三";
    }else if (_weekday == 5){
        weekStr = @"星期四";
    }else if (_weekday == 6){
        weekStr = @"星期五";
    }else if (_weekday == 7){
        weekStr = @"星期六";
    }
    return weekStr;
}