NSDate的NSDateComponents

Question

如何获取单个NSDate的NSDateComponents？我不想要两个日期之间的差异的组成部分，只是秒，分钟，小时，日，月和年的NSDate？

Answer 1

Apple docs中有一个示例，如清单3所示:获取日期组件

NSDate *today = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc]
                         initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *weekdayComponents =
                    [gregorian components:(NSDayCalendarUnit | 
                                           NSWeekdayCalendarUnit) fromDate:today];
NSInteger day = [weekdayComponents day];
NSInteger weekday = [weekdayComponents weekday];

请注意，在调用components方法时，您必须将所需的calendar units“或”在一起。

Answer 2

使用NSCalendar的方法：

- (NSDateComponents *)components:(NSUInteger)unitFlags fromDate:(NSDate *)date

像这样：

unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
NSDate *date = [NSDate date];


NSCalendar * cal = [NSCalendar currentCalendar];
NSDateComponents *comps = [cal components:unitFlags fromDate:date];

Answer 3

根据苹果开发人员文档，DateComponents具有second、minute、hour、day、month、year实例属性。下面的Swift 5Playground代码展示了如何使用DateComponents从Date实例中获取秒、分钟、小时、日、月和年组件

import Foundation

var calendar = Calendar(identifier: .gregorian)
calendar.timeZone = TimeZone(abbreviation: "CET")!
let date = Date()

// Get seconds, minutes, hours, day, month and year
let components = calendar.dateComponents([.second, .minute, .hour, .day, .month, .year], from: date)
let seconds = components.second
let minutes = components.minute
let hours = components.hour
let day = components.day
let month = components.month
let year = components.year

// Print components
print(String(describing: seconds)) // prints Optional(33)
print(String(describing: minutes)) // prints Optional(42)
print(String(describing: hours)) // prints Optional(22)
print(String(describing: day)) // prints Optional(17)
print(String(describing: month)) // prints Optional(12)
print(String(describing: year)) // prints Optional(2016)

/* ... */

// Set a formatter in order to display date
let formatter = DateFormatter()
formatter.dateStyle = .short
formatter.timeStyle = .long
formatter.timeZone = TimeZone(abbreviation: "CET")
formatter.locale = Locale(identifier: "fr_FR")
print(formatter.string(from: date)) // prints 17/12/2016 22:42:33 UTC+1