NSDate減去一個月

我想要兩個NSInteger年，月再去一個月。例如現在是2011-01我怎樣才能得到2010-12。增加是一回事，但我想減少。希望有人能幫助我一點。NSDate減去一個月

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];

招呼內

編輯：我的解決方案

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];

來源

2011-01-06 endo.anaconda

此示例代碼是從iPhone的日期和時間編程指南。

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);

我希望這有助於！

來源

2011-01-06 03:34:33 donkim

對不起，當我即將與您的解決方案即時獲得：4021-12-12 08:32:40 +0000 – 2011-01-06 03:47:56

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];

來源

2011-01-06 03:28:43 Penang

Np個！編輯：固定月份在邊緣情況 – Penang 2011-01-06 04:58:01

雖然接受的答案有效，但它使用iOS 8.0中折舊的代碼。另一種方式做同樣的事情，而不使用過時的代碼如下：

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

來源

2015-12-21 19:42:19 ChrisStillwell

我建議創建用於此目的的擴展：

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) 
    } 

}

用法：

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

來源

2017-02-20 16:16:18

NSDate減去一個月

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