OC中关于日期与时间的处理

在我们的开发中与日期打交道是常有的事情,OC中提供了NSDate和NSCalendar来给我们进行时间相关的处理与操作,还是非常容易的,下面我们就一起看一看.

1.NSDate基本概念

NSDate可以用来表示时间, 可以进行一些常见的日期\时间处理,一个NSDate对象就代表一个时间

• 获取系统当前时间
  NSDate *now = [NSDate date];

• 获取系统当前时间戳
  NSTimeInterval nowTimestamp = [[NSDate date] timeIntervalSince1970] * 1000.0;

• 计算时间间隔
  NSDate *myDate = [now timeIntervalSinceDate:otherDate];

    NSDate *now = [NSDate date];
    NSLog(@"now = %@", now);

     // 设置转换后的目标日期时区
     NSTimeZone *zone = [NSTimeZone systemTimeZone];

     // 得到源日期与世界标准时间的偏移量
     NSInteger interval = [zone secondsFromGMTForDate: date];
     NSLog(@"interval = %lu", interval);

     // 在当前时间基础上追加时区差值
     now = [now dateByAddingTimeInterval:interval];
     NSLog(@"%@", date);

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2.格式化日期

• NSDate -> NSString

    // 1.创建时间
    NSDate *now = [NSDate date];
    // 2.创建时间格式化
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    // 3.指定格式
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    // 4.格式化时间
    NSString *str = [formatter stringFromDate:now];
    NSLog(@"%@", str);

• NSString -> NSDate

    NSString *str = @"2015-06-28 19:53:24";

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

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

    NSDate *date = [formatter dateFromString:str];

    NSLog(@"%@", date);

• 解析 欧美格式 日期字符串

- (void)fmt_string_to_date2{
    // 服务器返回的时间字符串
    NSString *string = @"Tue May 31 17:46:55 +0800 2011";

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

    formatter.dateFormat = @"EEE MMM dd HH:mm:ss ZZZZ yyyy";
    
    NSDate * date = [formatter dateFromString:string];

    NSLog(@"%@", date);
}

• timestamp -> NSDate

// 解析 时间戳

- (void)fmt_string_to_date3{
    // 时间戳: 从1970年1月1日开始经历的毫秒数
    NSInteger timestamp = 1445164401875.157959;

    // 获取系统当前的时间戳
//    NSTimeInterval nowTimestamp = [[NSDate date] timeIntervalSince1970] * 1000.0;

    NSDate *date = [NSDate dateWithTimeIntervalSince1970:timestamp/1000.0];

    NSLog(@"%@", date);
}

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3.日期时间对象

结合NSCalendar和NSDate能做更多的 日期\时间 处理

• 获得NSCalendar对象
  NSCalendar *calendar = [NSCalendar currentCalendar];

• 获得年月日
  - (NSDateComponents *)components:(NSCalendarUnit)unitFlags fromDate:(NSDate *)date;

    NSDate *date = [NSDate date];
    // 1.创建日历对象
    NSCalendar *calendar = [NSCalendar currentCalendar];

    // 2.利用日历对象获取年月日时分秒
    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;

    NSDateComponents *components =[calendar components:type fromDate:date];
    
    NSLog(@"year = %lu", cmps.year);
    NSLog(@"month = %lu", cmps.month);
    NSLog(@"day = %lu", cmps.day);
    NSLog(@"hour = %lu", cmps.hour);
    NSLog(@"minute = %lu", cmps.minute);
    NSLog(@"second = %lu", cmps.second);
    NSLog(@"date = %@", date);

• 比较两个日期的差距
  - (NSDateComponents *)components:(NSCalendarUnit)unitFlags fromDate:(NSDate *)startingDate toDate:(NSDate *)resultDate options:(NSCalendarOptions)opts;

    // 1.确定时间
    NSString *time1 = @"2015-06-23 12:18:15";
    NSString *time2 = @"2015-06-28 10:10:10";

    // 2.将时间转换为date
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    NSDate *date1 = [formatter dateFromString:time1];
    NSDate *date2 = [formatter dateFromString:time2];

    // 3.创建日历
    NSCalendar *calendar = [NSCalendar currentCalendar];
     NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;

    // 4.利用日历对象比较两个时间的差值
    NSDateComponents *cmps = [calendar components:unit fromDate:date1 toDate:date2 options:0];

    // 5.输出结果
    NSLog(@"两个时间相差%ld年%ld月%ld日%ld小时%ld分钟%ld秒", cmps.year, cmps.month, cmps.day, cmps.hour, cmps.minute, cmps.second);

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iOS8.0开始,NSCalendar增加了一些更为简单的判断日期的方法,如:

- (BOOL)isDate:(NSDate *)date1 equalToDate:(NSDate *)date2 toUnitGranularity:(NSCalendarUnit)unit;

- (BOOL)isDate:(NSDate *)date1 inSameDayAsDate:(NSDate *)date2;

- (BOOL)isDateInToday:(NSDate *)date;

- (BOOL)isDateInYesterday:(NSDate *)date;

- (BOOL)isDateInTomorrow:(NSDate *)date;

- (BOOL)isDateInWeekend:(NSDate *)date;

但是iOS8.0以前是没有这些方法的,为了更好的兼容iOS8.0以前的项目,我们可以人为的给NSDate类做一些扩展.(新建继承自NSDate的分类,在分类里扩展方法)
代码如下所示:

#import "NSDate+BSExtension.h"

@implementation NSDate (BSExtension)

/**
 *  是否是今天
 */
- (BOOL)isToday{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    // 获取时间
    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;
}

/**
 *  是否是昨天
 */
- (BOOL)isYesterday{
    // 生成只有年月日的日期对象
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    
    NSString *selfString = [fmt stringFromDate:self];
    NSDate *selfDate = [fmt dateFromString:selfString];
    
    NSString *nowString = [fmt stringFromDate:[NSDate date]];
    NSDate *nowDate = [fmt dateFromString:nowString];
    
    // 比较时间差
    NSCalendar *calendar = [NSCalendar currentCalendar];
    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;
}

/**
 *  是否是明天
 */
- (BOOL)isTomorrow{
    // 生成只有年月日的日期对象
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    
    NSString *selfString = [fmt stringFromDate:self];
    NSDate *selfDate = [fmt dateFromString:selfString];
    
    NSString *nowString = [fmt stringFromDate:[NSDate date]];
    NSDate *nowDate = [fmt dateFromString:nowString];
    
    // 比较时间差
    NSCalendar *calendar = [NSCalendar currentCalendar];
    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;
}

/**
 *  是否是今年
 */
- (BOOL)isThisYear{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    NSInteger selfYear = [calendar component:NSCalendarUnitYear fromDate:self];
    NSInteger nowYear = [calendar component:NSCalendarUnitYear fromDate:[NSDate date]];
    
    return selfYear == nowYear;
}

@end

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