如何計算當前月份/年份的天數

Question

是否有任何方法可用於NSDate/NSCalendar來計算當月和當年的天數？

我看到的唯一的東西就是獲取給定日期或兩個日期之間的天數。
這是唯一的方法嗎？

Answer 1

這裏是一個同時適用於幾個月甚至幾年的方法：

let calendar = NSCalendar.currentCalendar() 
let date = NSDate() 

// Calculate start and end of the current year (or month with `.Month`): 
var startOfInterval : NSDate? 
var lengthOfInterval = NSTimeInterval() 
calendar.rangeOfUnit(.Year, startDate: &startOfInterval, interval: &lengthOfInterval, forDate: date) 
let endOfInterval = startOfInterval!.dateByAddingTimeInterval(lengthOfInterval) 

// Compute difference in days: 
let days = calendar.components(.Day, fromDate: startOfInterval!, toDate: endOfInterval, options: []) 
print(days) 

（您可能需要添加一些錯誤檢查，而不是強行展開 自選）

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更新Swift 3：

let calendar = Calendar.current 
let date = Date() 

// Calculate start and end of the current year (or month with `.month`): 
let interval = calendar.dateInterval(of: .year, for: date)! 

// Compute difference in days: 
let days = calendar.dateComponents([.day], from: interval.start, to: interval.end).day! 
print(days) 

Answer 2

let date = NSDate() 
let cal = NSCalendar(calendarIdentifier:NSCalendarIdentifierGregorian)! 
let days = cal.rangeOfUnit(.Day, inUnit: .Month, forDate: date) 

print("\(days) in the month of \(date)")