现在在很多项目中，不会直接显示时间，很多时候都是显示“刚刚”,”XX分钟前”，等等字样，那么他们是怎么实现的呢 ？

.新建一个NSDate的类目：NSDate+XMGExtension

NSDate+XMGExtension.h 文件

#import <Foundation/Foundation.h>

@interface NSDate (XMGExtension)

-(NSDateComponents *)deltaFrom:(NSDate *)from;

/** 是否是今年 */

-(BOOL)isThisYear;

/** 是否是今天 */

-(BOOL)isToday;

/** 是否是昨天 */

-(BOOL)isYesterday;

@end

NSDate+XMGExtension.m

#import "NSDate+XMGExtension.h"

@implementation NSDate (XMGExtension)

-(NSDateComponents *)deltaFrom:(NSDate *)from{

    //    日历

    NSCalendar *calendar = [NSCalendar currentCalendar];

    //    比较时间

    NSCalendarUnit unit = NSCalendarUnitDay | NSCalendarUnitMonth |NSCalendarUnitYear | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond ;

    return [calendar components:unit fromDate:from toDate:self options:];

}

-(BOOL)isThisYear{

    //    日历

    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSInteger nowYear = [calendar component:NSCalendarUnitYear fromDate:[NSDate date]];

    NSInteger selfYear = [calendar component:NSCalendarUnitYear fromDate:self];

    return  nowYear == selfYear;

}

//-(BOOL)isToday{

//    //    日历

//    NSCalendar *calendar = [NSCalendar currentCalendar];

//

//    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;

//

//    NSDateComponents *nowCmps = [calendar components:unit fromDate:[NSDate date]];

//

//    NSDateComponents *selfCmps = [calendar components:unit fromDate:self];

//

//    return nowCmps.year == selfCmps.year

//    && nowCmps.month == selfCmps.month

//    && nowCmps.day == selfCmps.day;

//

//

//}

-(BOOL)isToday{

    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];

    fmt.dateFormat = @"yyyy-MM-dd";

    NSString *nowString = [fmt stringFromDate:[NSDate date]];

    NSString *selfString = [fmt stringFromDate:self];

    return [nowString isEqualToString:selfString];

}

-(BOOL)isYesterday{

    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];

    fmt.dateFormat = @"yyyy-MM-dd";

    NSDate *nowDate = [fmt dateFromString:[fmt stringFromDate:[NSDate date]]];

    NSDate *selfDate = [fmt dateFromString:[fmt stringFromDate:self]];

    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;

    NSDateComponents *cmps = [calendar components:unit fromDate:selfDate toDate:nowDate options:];

    return cmps.year ==

    && cmps.month ==

    && cmps.day == ;

}

@end

在model中使用 create_time getter方法

XMGTopic.h文件

/** 发帖时间 */

@property(nonatomic,copy)NSString *create_time;

XMGTopic.m文件

#import "XMGTopic.h"

@implementation XMGTopic

-(NSString *)create_time{

    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];

    fmt.dateFormat = @"yyyy-MM-dd HH:mm:ss";

    NSDate *create = [fmt dateFromString:_create_time];

    if (create.isThisYear) { //今年

        if (create.isToday) {   //今天

            NSDateComponents *cmps = [[NSDate date] deltaFrom:create];

            if (cmps.hour>=) { //时间差距>=1小时

                return [NSString stringWithFormat:@"%zd小时前",cmps.hour];

            }else if(cmps.minute>=){ //时间差距>=1分分钟

                return [NSString stringWithFormat:@"%zd分钟前",cmps.minute];

            }else{//时间差距<1分分钟

                return  @"刚刚";

            }

        }else if(create.isYesterday){  //昨天

            fmt.dateFormat= @"昨天 HH:mm";

            return [fmt stringFromDate:create];

        }else{

            fmt.dateFormat= @"MM-dd HH:mm";

            return  [fmt stringFromDate:create];

        }

    }else{ //不是今年

        return _create_time;

    }

}

@end

在view中XMGTopicCell.m文件中

-(void)setTopic:(XMGTopic *)topic{

    _topic = topic;

    topic.sina_v = arc4random_uniform()%;

//    新浪加V

    self.sinaVView.hidden = !topic.isSina_v;

//    设置头像

    [self.profileImageView sd_setImageWithURL:[NSURL URLWithString:topic.profile_image] placeholderImage:[UIImage imageNamed:@"defaultUserIcon"]];

//    设置昵称

    self.nameLabel.text = topic.name;

//    设置帖子的创建时间

    self.createTimeLabel.text = topic.create_time;

//    设置按钮文字

    [self setupButtonTitle:self.dingButtton count:topic.ding placeholder:@"顶"];

    [self setupButtonTitle:self.caiButton count:topic.cai placeholder:@"踩"];

    [self setupButtonTitle:self.shareButton count:topic.repost placeholder:@"分享"];

    [self setupButtonTitle:self.commentButton count:topic.comment placeholder:@"评论"];

}