使用Cocoa確定兩個日期之間的月數

Question

如何使用Cocoa計算兩個日期之間的月數？

感謝， 斯坦

Answer 1

看NSCalendars components:fromDate:toDate:options方法。它可以讓你減去日期，然後提取幾個月屬性值

Answer 2

NSInteger month = [[[NSCalendar currentCalendar] components: NSCalendarUnitMonth 
                fromDate: yourFirstDate 
                toDate: yourSecondDate 
                options: 0] month]; 

Answer 3

組件：FROM日期：TODATE：選擇不正確的以下示例工作：

開始日期：2012年1月1日 結束日期：3月31日，使用上述方法個月2012

NUM = 2

正確答案應爲3個月。

我用很長的計算方法如下： 1.查找開始月份的天數。將它添加到月份的小數部分。如果第一個日期是月初，請將其計爲整月。 2.找到月底的天數。將其添加到月份的小數部分如果日期是本月的最後一個月，則將其計爲整月。 3.查找2個日期之間的整個/整個月份並添加到月份的整數部分。 4.將月份的小數部分加上整數&以獲得正確的值。

Answer 4

要獲得包括每月的分數的回答以下可用於：

- (NSNumber *)numberOfMonthsBetweenFirstDate:(NSDate *)firstDate secondDate:(NSDate *)secondDate { 

if ([firstDate compare:secondDate] == NSOrderedDescending) { 
    return nil; 
} 

NSCalendar *calendar = [NSCalendar currentCalendar]; 

NSDateComponents *firstDateComponents = [calendar components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit 
                fromDate:firstDate]; 

NSInteger firstDay = [firstDateComponents day]; 

NSRange rangeOfFirstMonth = [calendar rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:firstDate]; 
NSUInteger numberOfDaysInFirstMonth = rangeOfFirstMonth.length; 
CGFloat firstMonthFraction = (CGFloat)(numberOfDaysInFirstMonth - firstDay)/(CGFloat)numberOfDaysInFirstMonth; 

// last month component 
NSDateComponents *lastDateComponents = [calendar components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit 
                   fromDate:secondDate]; 
NSInteger lastDay = [lastDateComponents day]; 
NSRange rangeOfLastMonth = [calendar rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:secondDate]; 
NSUInteger numberOfDaysInLastMonth = rangeOfLastMonth.length; 
CGFloat lastMonthFraction = (CGFloat)(lastDay)/(CGFloat)numberOfDaysInLastMonth; 

// Check if the two dates are within the same month 
if (firstDateComponents.month == lastDateComponents.month 
     && firstDateComponents.year == lastDateComponents.year) { 
    NSDateComponents *dayComponents = [calendar components:NSDayCalendarUnit 
                  fromDate:firstDate 
                  toDate:secondDate 
                  options:0]; 

    NSRange rangeOfMonth = [calendar rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:firstDate]; 
    NSUInteger numberOfDaysInMonth = rangeOfMonth.length; 
    return [NSNumber numberWithFloat:(CGFloat)dayComponents.day/(CGFloat)numberOfDaysInMonth]; 
} 

// Start date of the first complete month 
NSDateComponents *firstDateFirstDayOfNextMonth = firstDateComponents; 
firstDateFirstDayOfNextMonth.month +=1; 
firstDateFirstDayOfNextMonth.day = 1; 

// First day of the last month 
NSDateComponents *secondDateFirstDayOfMonth = lastDateComponents; 
secondDateFirstDayOfMonth.day = 1; 

NSInteger numberOfMonths = secondDateFirstDayOfMonth.month - firstDateFirstDayOfNextMonth.month 
     + (secondDateFirstDayOfMonth.year - firstDateFirstDayOfNextMonth.year) * 12; 

return [NSNumber numberWithFloat:(firstMonthFraction + numberOfMonths + lastMonthFraction)]; 
} 

Answer 5

我不得不計算兩個日期之間的月變化。這意味着，從一月份的31日至2月1日本月1日已通過了NSCalendar.components將返回0

import UIKit 

func monthsSince(from: NSDate, to: NSDate) -> Int { 
    let fromComponents = NSCalendar.currentCalendar().components([.Month, .Year], fromDate: from) 
    let toComponents = NSCalendar.currentCalendar().components([.Month, .Year], fromDate: to) 

    return ((toComponents.year - fromComponents.year) * 12) + (toComponents.month - fromComponents.month) 
} 

let tests = [ 
    (from: (day: 1, month: 1, year: 2016), to: (day: 31, month: 1, year: 2016), result: 0), 
    (from: (day: 22, month: 1, year: 2016), to: (day: 5, month: 2, year: 2016), result: 1), 
    (from: (day: 22, month: 12, year: 2015), to: (day: 1, month: 1, year: 2016), result: 1), 
    (from: (day: 1, month: 1, year: 2016), to: (day: 1, month: 2, year: 2016), result: 1), 
    (from: (day: 1, month: 1, year: 2016), to: (day: 1, month: 3, year: 2016), result: 2) 
] 

for test in tests { 
    let from = NSCalendar.currentCalendar().dateWithEra(1, year: test.from.year, month: test.from.month, day: test.from.day, hour: 0, minute: 0, second: 0, nanosecond: 0)! 
    let to = NSCalendar.currentCalendar().dateWithEra(1, year: test.to.year, month: test.to.month, day: test.to.day, hour: 0, minute: 0, second: 0, nanosecond: 0)! 

    if monthsSince(from, to: to) == test.result { 
     print("Test \(test), Passed!") 
    } else { 
     print("Test \(test), Failed!") 
    } 
}