iOS之NSDate

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1.NSDate的详细介绍

//1.通过date方法创建出来的对象,就是当前时间对象;
NSDate *date = [NSDate date];
NSLog(@"now = %@", date);
 
//2.获取当前所处时区
NSTimeZone *zone = [NSTimeZone systemTimeZone];
NSLog(@"now = %@", zone);
 
//3.获取当前时区和指定时间差
NSInteger seconds = [zone secondsFromGMTForDate:date];
NSLog(@"seconds = %lu", seconds);
 
NSDate *nowDate = [date dateByAddingTimeInterval:seconds];
NSLog(@"nowDate = %@", nowDate);
 
//4.获取当前时间  NSDate --> NSStringNSDate *date = [NSDate date];
 
//创建一个时间格式化对象
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
 
//按照什么样的格式来格式化时间
formatter.dateFormat = @"yyyy年MM月dd日 HH时mm分ss秒 Z";
formatter.dateFormat = @"yyyy/MM/dd HH/mm/ss Z";
formatter.dateFormat = @"MM-dd-yyyy HH-mm-ss";
 
NSString *res = [formatter stringFromDate:date];

2.字符串转时间

    // 时间字符串NSString *str = @"2014-03-11 06:44:11 +0800";
 
    // 1.创建一个时间格式化对象NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
 
    // 2.格式化对象的样式/z大小写都行/格式必须严格和字符串时间一样
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss Z";
 
    // 3.利用时间格式化对象让字符串转换成时间 (自动转换0时区/东加西减)NSDate *date = [formatter dateFromString:str];
 
    NSLog(@"%@",date);

3.时间转换成字符串

    NSDate *now = [NSDate date];
 
    // 1.创建一个时间格式化对象NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
 
    // 2.设置时间格式化对象的样式
    formatter.dateFormat = @"yyyy年MM月dd日 HH时mm分ss秒 +0800";
 
    // 3.利用时间格式化对象对时间进行格式化NSString *str = [formatter stringFromDate:now];
 
    NSLog(@"%@",str);

4.利用日历比较两个时间的差值

    // 时间字符串NSString *str = @"2012-03-11 06:44:11 +0800";
 
    // 1.创建一个时间格式化对象NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
 
    // 2.格式化对象的样式/z大小写都行/格式必须严格和字符串时间一样
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss Z";
 
    // 3.字符串转换成时间/自动转换0时区/东加西减NSDate *date = [formatter dateFromString:str];
    NSDate *now = [NSDate date];
 
   // 注意获取calendar,应该根据系统版本判断NSCalendar *calendar = [NSCalendar currentCalendar];
 
    NSCalendarUnit type = NSCalendarUnitYear |
    NSCalendarUnitMonth |
    NSCalendarUnitDay |
    NSCalendarUnitHour |
    NSCalendarUnitMinute |
    NSCalendarUnitSecond;
 
    // 4.获取了时间元素NSDateComponents *cmps = [calendar components:type fromDate:date toDate:now options:0];
 
    NSLog(@"%ld年%ld月%ld日%ld小时%ld分钟%ld秒钟", cmps.year, cmps.month, cmps.day, cmps.hour, cmps.minute, cmps.second);

5.日期比较

// 时间字符串NSString *createdAtString = @"2015-11-20 11:10:05";
NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
fmt.dateFormat = @"yyyy-MM-dd HH:mm:ss";
NSDate *createdAtDate = [fmt dateFromString:createdAtString];
 
// 手机当前时间NSDate *nowDate = [NSDate date];
 
/**
 NSComparisonResult的取值
 NSOrderedAscending = -1L, // 升序, 越往右边越大
 NSOrderedSame,  // 相等
 NSOrderedDescending // 降序, 越往右边越小
 */// 获得比较结果(谁大谁小)NSComparisonResult result = [nowDate compare:createdAtDate];
if (result == NSOrderedAscending) { // 升序, 越往右边越大NSLog(@"createdAtDate > nowDate");
} else if (result == NSOrderedDescending) { // 降序, 越往右边越小NSLog(@"createdAtDate < nowDate");
} else {
    NSLog(@"createdAtDate == nowDate");
}

6.NSDate的使用注意

时间戳:从1970年1月1号 00:00:00开始走过的毫秒数
注意:1秒==1000毫秒

// 时间字符串 -> 时间戳NSString *string = @"1745645645645";
NSTimeInterval second = string.longLongValue / 1000.0;
 
// 时间戳 -> NSDate *NSDate *date = [NSDate dateWithTimeIntervalSince1970:second];
NSLog(@"%@", date);

//注意:使用[NSCalendar currentCalendar],iOS8以后会有bug,要加判断
// 判断方法一:// 宏书写注意:建议不要全是小写,要有大写,否则书写时候参数有ken'neng不提示#define iOS(version) ([UIDevice currentDevice].systemVersion.doubleValue >= (version))NSCalendar *calendar = nil;
if ([UIDevice currentDevice].systemVersion.doubleValue >= 8.0) {
    calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
} else {
    calendar = [NSCalendar currentCalendar];
}
 
// 判断方法二:NSCalendar *calendar = nil;
// NSCalendar不提示这个respondsToSelector:方法,但是的确有这个方法if ([NSCalendar respondsToSelector:@selector(calendarWithIdentifier:)]) {
    calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
} else {
    calendar = [NSCalendar currentCalendar];
}

7.项目开发中常用的时间日期分类

#import <Foundation/Foundation.h>
@interface NSDate (DXExtension)
- (BOOL)isThisYear;
- (BOOL)isToday;
- (BOOL)isYesterday;
- (BOOL)isInOneMinute;
- (BOOL)isInOneHour;
- (BOOL)isTomorrow;
@end

@implementation NSDate (DXExtension)
static NSDateFormatter *formatter_;
static  NSCalendar *calendar_;
 
// 第一次使用这个类的时候调用
// 优化性能,减少频繁的创建格式化对象
+ (void)initialize
{
    formatter_ = [[NSDateFormatter alloc] init];
    calendar_ = [NSCalendar calendar];
}
- (BOOL)isToday
{
    formatter_.dateFormat = @"yyyyMMdd";
 
    NSString *selfDay = [formatter_ stringFromDate:self];
    NSString *nowDay = [formatter_ stringFromDate:[NSDate date]];
 
    return [selfDay isEqualToString:nowDay];
}
 
- (BOOL)isYesterday
{
    formatter_.dateFormat = @"yyyyMMdd";
 
    NSString *selfDay = [formatter_ stringFromDate:self];
    NSString *nowDay = [formatter_ stringFromDate:[NSDate date]];
 
    NSDate *selfDate = [formatter_ dateFromString:selfDay];
    NSDate *nowDate = [formatter_ dateFromString:nowDay];
 
    NSCalendarUnit units = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    NSDateComponents *cmp = [calendar_ components:units fromDate:nowDate toDate:selfDate options:0];
 
    return cmp.year == 0 && cmp.month == 0 && cmp.day == 1;
}
 
- (BOOL)isTomorrow
{
    formatter_.dateFormat = @"yyyyMMdd";
 
    NSString *selfDay = [formatter_ stringFromDate:self];
    NSString *nowDay = [formatter_ stringFromDate:[NSDate date]];
 
    NSDate *selfDate = [formatter_ dateFromString:selfDay];
    NSDate *nowDate = [formatter_ dateFromString:nowDay];
 
    NSCalendarUnit units = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
    NSDateComponents *cmp = [calendar_ components:units fromDate:nowDate toDate:selfDate options:0];
 
    return cmp.year == 0 && cmp.month == 0 && cmp.day == -1;
}
 
- (BOOL)isThisYear
{
    formatter_.dateFormat = @"yyyy";
    NSString *selfYear = [formatter_ stringFromDate:self];
    NSString *currentYear = [formatter_ stringFromDate:[NSDate date]];
 
    return [selfYear isEqualToString:currentYear];
}
- (BOOL)isInOneMinute
{
    formatter_.dateFormat = @"yyyyMMddHHmm";
 
    NSString *selfSecond = [formatter_ stringFromDate:self];
    NSString *nowSecond = [formatter_ stringFromDate:[NSDate date]];
 
    return [selfSecond isEqualToString:nowSecond];
}
 
- (BOOL)isInOneHour
{
    formatter_.dateFormat = @"yyyyMMddHH";
 
    NSString *selfHour = [formatter_ stringFromDate:self];
    NSString *nowHour = [formatter_ stringFromDate:[NSDate date]];
 
    return [selfHour isEqualToString:nowHour];
 
}
@end

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