Question

基本上，我想弄清楚它是否是第二天。因此，我将当前日期（例如1月2日）不断存储在plist中。但是下次用户打开应用程序时，如果日期已经改变（例如1月3日），我想做点什么。请注意，简单的升序检查不起作用，因为我不想知道一个日期是否晚于另一个日期，如果差异仅以小时为单位。我需要能够区分1月2日11:50和1月3日2:34而不是1月3日2:34和1月3日5:12。

Answer 1

我使用以下内容找到了SO：

- (BOOL)isSameDay:(NSDate*)date1 otherDay:(NSDate*)date2 {
    NSCalendar* calendar = [NSCalendar currentCalendar];

    unsigned unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    NSDateComponents* comp1 = [calendar components:unitFlags fromDate:date1];
    NSDateComponents* comp2 = [calendar components:unitFlags fromDate:date2];

    return [comp1 day]   == [comp2 day] &&
    [comp1 month] == [comp2 month] &&
    [comp1 year]  == [comp2 year];
}

Answer 2

查看Date Time Programming Guide为您提供了一个如何按组件计算两个日期之间差异的示例：例如：

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];

Answer 3

我的版本基于Neils'（警告：未经测试）：

Mine与NSDate上的- (NSComparisonResult)compare:更相似。要检查天数相等，请执行[myDate compareDayMonthAndYear:otherDate] == NSOrderedSame

- (NSComparisonResult)compareDayMonthAndYear:(NSDate *)date
{
    NSCalendar *calendar = [NSCalendar currentCalendar];

    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    NSDateComponents *selfComponents = [calendar components:unitFlags fromDate:self];
    NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:date];

    BOOL dayIsEqual = (selfComponents.day == dateComponents.day && selfComponents.month == dateComponents.month && selfComponents.year == dateComponents.year);
    if (dayIsEqual) {
        return NSOrderedSame;
    }
    return [self compare:date];
}

Answer 4

使用NSCalendarDate代替NSDate，并比较它们从-dayOfCommonEra返回的内容

@implementation NSDate (sameDayOrNot)

- (BOOL) sameDayAsDate:(NSDate *) otherDate
{
NSCalendarDate *date1 = [[NSCalendarDate alloc] initWithTimeInterval:0 sinceDate:self];
NSCalendarDate *date2 = [[NSCalendarDate alloc] initWithTimeInterval:0 sinceDate:otherDate];
BOOL result = ([date1 dayOfCommonEra] == [date2 dayOfCommonEra]);
[date1 release];
[date2 release];
return result;
}

@end

如何比较可可的两个日期（仅限日期;不是时间）？

4 个答案: