檢查指定日期是今天，昨天還是未來日期

Question

我有一個關於NSDate的查詢。我有一個日期，即「2011-10-04 07:36:38 +0000」，我想檢查這個日期是否是昨天，或者今天或未來的日期。

我該怎麼辦？

Answer 1

試試這個：

注意：根據您的需要更改日期格式。

NSDateFormatter* df = [[NSDateFormatter alloc] init]; 
[df setDateFormat:@"MM/dd/yyyy"]; 
NSDate* enteredDate = [df dateFromString:@"10/04/2011"]; 
NSDate * today = [NSDate date]; 
NSComparisonResult result = [today compare:enteredDate]; 
switch (result) 
{ 
    case NSOrderedAscending: 
     NSLog(@"Future Date"); 
        break; 
    case NSOrderedDescending: 
     NSLog(@"Earlier Date"); 
        break; 
    case NSOrderedSame: 
     NSLog(@"Today/Null Date Passed"); //Not sure why This is case when null/wrong date is passed 
        break; 
} 

Answer 2

使用任何如下因素根據烏拉圭回合的需要，

– earlierDate: 
– laterDate: 
– compare: 

請參閱本http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSDate_Class/Reference/Reference.html

Answer 3

見Apple's documentation on date calculations：

NSDate *startDate = ...; 
NSDate *endDate = ...; 

NSCalendar *gregorian = [[NSCalendar alloc] 
       initWithCalendarIdentifier:NSGregorianCalendar]; 

NSUInteger unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit; 

NSDateComponents *components = [gregorian components:unitFlags 
              fromDate:startDate 
              toDate:endDate options:0]; 
NSInteger months = [components month]; 
NSInteger days = [components day]; 

如果days是+1和-1，那麼您的日期之間是「今天」的候選人。顯然你需要考慮你如何處理小時。推測最簡單的方法是將所有日期設置爲當天00:00時（truncate the date using an approach like this），然後使用這些值進行計算。這樣你今天得到0，昨天得到-1，明天得+1，而其他任何價值都會告訴你未來或過去有多遠。

Answer 4

-(NSString*)timeAgoFor:(NSString*)tipping_date 
{ 
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; 
    [dateFormatter setDateFormat:@"yyyy-MM-dd"]; 
    NSDate *date = [dateFormatter dateFromString:tipping_date]; 
    NSString *key = @""; 
    NSTimeInterval ti = [date timeIntervalSinceDate:[NSDate date]]; 
    key = (ti > 0) ? @"Left" : @"Ago"; 

    ti = ABS(ti); 
    NSDate * today = [NSDate date]; 
    NSComparisonResult result = [today compare:date]; 

    if (result == NSOrderedSame) { 
     return[NSString stringWithFormat:@"Today"]; 
    } 
    else if (ti < 86400 * 2) { 
     return[NSString stringWithFormat:@"1 Day %@",key]; 
    }else if (ti < 86400 * 7) { 
     int diff = round(ti/60/60/24); 
     return[NSString stringWithFormat:@"%d Days %@", diff,key]; 
    }else { 
     int diff = round(ti/(86400 * 7)); 
     return[NSString stringWithFormat:@"%d Wks %@", diff,key]; 
    } 
}