iphone - iOS 中当年的天数

Question

我想找出今天是当年的天数。例如，如果今天是 2012 年 3 月 15 日，我应该得到 75(31 + 29 + 15)。或者我们可以简单地说今天和当年 Jan01 之间的天数。

Answer 1

使用 的ordinalityOfUnit方法NSCalendar获取一年中的天数 - 指定NSDayCalendarUnit inUnit:NSYearCalendarUnit

迅速

let calendar: Calendar = .autoupdatingCurrent
let dayOfTheYear = calendar.ordinality(of: .day, in: .year, for: Date())

Objective-C

NSCalendar *currentCalendar = [NSCalendar currentCalendar];
NSDate *today = [NSDate date];
NSInteger dc = [currentCalendar  
    ordinalityOfUnit:NSDayCalendarUnit 
    inUnit:NSYearCalendarUnit 
    forDate:today
];

2012 年 9 月 25 日为 269

Answer 2

使用NSDateComponents您可以收集NSDayCalendarUnit应指示当前日期的组件。

以下内容应该适合您的需求：

//create calendar
NSCalendar *calendar = [NSCalendar currentCalendar];

//set calendar time zone
[calendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];

//gather date components
NSDateComponents *components = [calendar components:NSDayCalendarUnit fromDate:[NSDate date]];

//gather time components
NSInteger day = [components day];

Answer 3

根据数据格式参考，可以使用说明D符来表示一年中的哪一天。如果您想执行一些计算，日期格式化程序不是很有帮助，但如果您只想显示一年中的哪一天，这可能是最简单的方法。代码看起来像：

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateFormatter *df = [[NSDateFormatter alloc] init];

[df setCalendar:cal];
[df setDateFormat:@"DDD"];    // D specifier used for day of year
NSString *dayOfYearString = [df stringFromDate:someDate];  // you choose 'someDate'

NSLog(@"The day is: %@", dayOfYearString);

Answer 4

使用NSDate,NSDateComponents和NSCalendar类，您可以很容易地计算上一年的最后一天和今天之间的天数（这与计算当年的今天数字相同）：

// create your NSDate and NSCalendar objects
NSDate *today = [NSDate date];
NSDate *referenceDate;
NSCalendar *calendar = [NSCalendar currentCalendar];

// get today's date components
NSDateComponents *components = [calendar components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:today];

// changing the date components to the 31nd of December of last year
components.day = 31;
components.month = 12;
components.year--;

// store these components in your date object
referenceDate = [calendar dateFromComponents:components];

// get the number of days from that date until today
components = [calendar components:NSDayCalendarUnit fromDate:referenceDate toDate:[NSDate date] options:0];
NSInteger days = components.day;