iOS 之NSDate的Category

判断日期是是否是今年？今天？

NSDate+Extension.h

#import <Foundation/Foundation.h>
@interface NSDate (Extension)

//比较from和self的时间差值
- (NSDateComponents *)deltaFrom:(NSDate *)from;

 //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;

@end

NSDate+Extension.m

#import "NSDate+Extension.h"

@implementation NSDate (Extension)
- (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:0];
}

- (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
{
    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
{
    // 2014-12-31 23:59:59 -> 2014-12-31
    // 2015-01-01 00:00:01 -> 2015-01-01
    
    // 日期格式化类
    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];
    NSDateComponents *cmps = [calendar components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear 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 = @"yyyy-MM-dd";
    
    NSDate *nowDate = [fmt dateFromString:[fmt stringFromDate:[NSDate date]]];
    NSDate *selfDate = [fmt dateFromString:[fmt stringFromDate:self]];
    
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *cmps = [calendar components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:nowDate toDate:selfDate options:0];
    
    return cmps.year == 0
    && cmps.month == 0
    && cmps.day == 1;

}
@end

简单使用TopicModel

#import "TopicModel.m"文件中

- (NSString *)create_time
{
    // 日期格式化类
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    // 设置日期格式(y:年,M:月,d:日,H:时,m:分,s:秒)
    fmt.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    // 帖子的创建时间
    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 >= 1) { // 时间差距 >= 1小时
                return [NSString stringWithFormat:@"%zd小时前", cmps.hour];
            } else if (cmps.minute >= 1) { // 1小时 > 时间差距 >= 1分钟
                return [NSString stringWithFormat:@"%zd分钟前", cmps.minute];
            } else { // 1分钟 > 时间差距
                return @"刚刚";
            }
        } else if (create.isYesterday) { // 昨天
            fmt.dateFormat = @"昨天 HH:mm:ss";
            return [fmt stringFromDate:create];
        } else if(creat.isTomorrow){
            fmt.dateFormat = @"明天 HH:mm:ss";
            return [fmt stringFromDate:create];
        }else { // 其他
            fmt.dateFormat = @"MM-dd HH:mm:ss";
            return [fmt stringFromDate:create];
        }
    } else { // 非今年
        return _create_time;
    }
}