NSDate から 1 か月を差し引く

Question

2 NSInteger 年、月を 1 か月前に戻したいと思います。例えば今は 2011-01 どうすれば入手することができますか 2010-12. 。足すことも大事ですが、引き算もしたいのです。

NSDate *date = [NSDate date];
NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:date];
NSInteger year = [dateComponents year];
NSInteger month = [dateComponents month];
[calendar release];
NSString * pdf_name = [NSString stringWithFormat:@"file_%d_%02d.pdf", year, month];

遠藤さんに挨拶します

編集：私の解決策

    NSCalendar *calendar= [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
 NSCalendarUnit unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

 NSDate *date = [NSDate date];
 NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:date];
 NSInteger year = [dateComponents year];
 NSInteger month = [dateComponents month];

 BOOL substractOneMonth = YES;
 if (substractOneMonth) {
  if (month==1) {
   year--;
   month = 12;
  }else {
   month--;
  }
 }
 [calendar release];

 NSString * pdf_name = [NSString stringWithFormat:@"file_%d_%02d.pdf", year, month];

Answer 1

このサンプルコードは、プログラミングガイドiPhoneの日付と時刻からです。

NSDate *today = [[NSDate alloc] init];
NSLog(@"%@", today);
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
[offsetComponents setMonth:-1]; // note that I'm setting it to -1
NSDate *endOfWorldWar3 = [gregorian dateByAddingComponents:offsetComponents toDate:today options:0];
NSLog(@"%@", endOfWorldWar3);

私はこのことができます願っています！

Answer 2

は受け入れ答えの作品が、それは、iOS 8.0で非推奨のコードを使用しています。次のように非推奨のコードを使用せずに同じことを行う別の方法があります：

NSDate *date = [NSDate date];
NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
[dateComponents setMonth:-1];
date = [[NSCalendar currentCalendar] dateByAddingComponents:dateComponents toDate:date options:0];

Answer 3

私は、この目的のために拡張を作成勧めます：

extension Date {

    func adding(months: Int) -> Date? {
        let calendar = Calendar(identifier: .gregorian)

        var components = DateComponents()
        components.calendar = calendar
        components.timeZone = TimeZone(secondsFromGMT: 0)
        components.month = months

        return calendar.date(byAdding: components, to: self)
    }

}

使用方法：

let now = Date()
let sixMonthsBefore = now.adding(months: -6)
let threeMonthsAfter = now.adding(months: 3)

Answer 4

NSDate *date = [NSDate date];
NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:date];
NSInteger year = [dateComponents year];
NSInteger month = [dateComponents month];

month -= month - 1;

if (month < 1) {
 year -= 1;
 month = 12;
}

[calendar release];
NSString * pdf_name = [NSString stringWithFormat:@"file_%d_%02d.pdf", year, month];