判断日期是今天昨天明天

这个主要是从网上看到的 感觉非常好打算保存起来

-(NSString *)compareDate:(NSDate *)date{

    NSTimeInterval secondsPerDay = 24 * 60 * 60;
    NSDate *today = [[NSDate alloc] init];
    NSDate *tomorrow, *yesterday;

    tomorrow = [today dateByAddingTimeInterval: secondsPerDay];
    yesterday = [today dateByAddingTimeInterval: -secondsPerDay];

// 10 first characters of description is the calendar date:
    NSString * todayString = [[today description] substringToIndex:10];
    NSString * yesterdayString = [[yesterday description] substringToIndex:10];
    NSString * tomorrowString = [[tomorrow description] substringToIndex:10];

    NSString * dateString = [[date description] substringToIndex:10];

    if ([dateString isEqualToString:todayString])
    {
        return @"今天";
    } else if ([dateString isEqualToString:yesterdayString])
    {
        return @"昨天";
    }else if ([dateString isEqualToString:tomorrowString])
    {
        return @"明天";
    }
    else
    {
        return dateString;
    }
}