我们会在发朋友圈时候，会有个时间显示，这种时间显示和我上午给大家封装的不一样，上午的是那种显示具体时间。可是有时候我们产品需求是和微信一样显示
比如：这种需求

@"刚刚" \ @"10分钟前" \ @"5小时前" \ @"昨天 09:10:05" \ @"11-20 09:10:05" \ @"2016-8-10 04:10:05"

开始

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第一步：

Snip20160810_3.png

+ (instancetype)calendar;

第二步：

Snip20160810_4.png

+ (instancetype)calendar
{
    if ([NSCalendar respondsToSelector:@selector(calendarWithIdentifier:)]) {
        return [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
    } else {
        return [NSCalendar currentCalendar];
    }

}

第三步：

Snip20160810_5.png

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/**
 *  是否为今年
 */
- (BOOL)isThisYear;

/**
 *  是否为今天
 */
- (BOOL)isToday;

/**
 *  是否为昨天
 */
- (BOOL)isYesterday;

/**
 *  是否为明天
 */
- (BOOL)isTomorrow;

第四步：

Snip20160810_8.png

Snip20160810_9.png

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- (BOOL)isThisYear
{
    // 判断self这个日期是否为今年
    NSCalendar *calendar = [NSCalendar calendar];
    
    // 年
    NSInteger selfYear = [calendar component:NSCalendarUnitYear fromDate:self];
    NSInteger nowYear = [calendar component:NSCalendarUnitYear fromDate:[NSDate date]];
    
    return selfYear == nowYear;
}
//- (BOOL)isThisYear
//{
//    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
//    fmt.dateFormat = @"yyyy";
//    
//    // 年
//    NSString *selfYear = [fmt stringFromDate:self];
//    NSString *nowYear = [fmt stringFromDate:[NSDate date]];
//    
//    return [selfYear isEqualToString:nowYear];
//}
- (BOOL)isToday
{
    // 判断self这个日期是否为今天
    NSCalendar *calendar = [NSCalendar calendar];
    
    // 获得年月日元素
    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    NSDateComponents *selfCmps = [calendar components:unit fromDate:self];
    NSDateComponents *nowCmps = [calendar components:unit fromDate:[NSDate date]];
    
    return selfCmps.year == nowCmps.year
    && selfCmps.month == nowCmps.month
    && selfCmps.day == nowCmps.day;
}

//- (BOOL)isToday
//{
//    // 判断self这个日期是否为今天
//    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
//    fmt.dateFormat = @"yyyyMMdd";
//
//    NSString *selfString = [fmt stringFromDate:self];
//    NSString *nowString = [fmt stringFromDate:[NSDate date]];
//
//    return [selfString isEqualToString:nowString];
//}

- (BOOL)isYesterday
{
    // 判断self这个日期是否为昨天
    
    // self == 2015-10-31 23:07:08 -> 2015-10-31 00:00:00
    // now  == 2015-11-01 14:39:20 -> 2015-11-01 00:00:00
    
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyyMMdd";
    
    NSString *selfString = [fmt stringFromDate:self]; // 20151031
    NSString *nowString = [fmt stringFromDate:[NSDate date]]; // 20151101
    
    NSDate *selfDate = [fmt dateFromString:selfString]; // 2015-10-31 00:00:00
    NSDate *nowDate = [fmt dateFromString:nowString]; // 2015-11-01 00:00:00
    
    NSCalendar *calendar = [NSCalendar calendar];
    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    NSDateComponents *cmps = [calendar components:unit fromDate:selfDate toDate:nowDate options:0];
    
    return cmps.year == 0
    && cmps.month == 0
    && cmps.day == 1;
}

- (BOOL)isTomorrow
{
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyyMMdd";
    
    NSString *selfString = [fmt stringFromDate:self]; // 20151031
    NSString *nowString = [fmt stringFromDate:[NSDate date]]; // 20151101
    
    NSDate *selfDate = [fmt dateFromString:selfString]; // 2015-10-31 00:00:00
    NSDate *nowDate = [fmt dateFromString:nowString]; // 2015-11-01 00:00:00
    
    NSCalendar *calendar = [NSCalendar calendar];
    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    NSDateComponents *cmps = [calendar components:unit fromDate:selfDate toDate:nowDate options:0];
    
    return cmps.year == 0
    && cmps.month == 0
    && cmps.day == -1;
}