Ios 如何将格式为HH:MM:SS的字符串转换为NSDate？

json responce中以字符串格式HH:MM:SS存储的时间。我想将其转换为本地通知的NSDate。 尝试 NSString*datestr=@“21:00:00”

---

获取零时间。我有json的时间格式是21:00:00格式，只是没有日期。我想为每天的本地通知设置这个时间。

如果字符串的小时数部分在0到23之间，则需要使用

HH

然后，您需要将日期转换为

NSDateComponents

，以便创建

UNCalendarNotificationTrigger

@implementation ViewController {
    NSDateFormatter *parser;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    parser = [[NSDateFormatter alloc] init];
    parser.dateFormat = @"HH:mm:ss";
    parser.calendar = [NSCalendar autoupdatingCurrentCalendar];
}

- (void)createRepeatingNotificationAtTimeOfDay:(NSString *)timeOfDay {
    NSDate *date = [parser dateFromString:timeOfDay];
    if (date == nil) {
        // Couldn't parse the string.
        return;
    }

    NSDateComponents *components = [parser.calendar components:NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond fromDate:date];
    if (components == nil) {
        // Couldn't extract components.
        return;
    }

    UNCalendarNotificationTrigger *trigger = [UNCalendarNotificationTrigger triggerWithDateMatchingComponents:components repeats:YES];
    UNMutableNotificationContent *content = [[UNMutableNotificationContent alloc] init];
    content.title = @"Daily alarm";
    UNNotificationRequest *request = [UNNotificationRequest requestWithIdentifier:@"dailyalarm" content:content trigger:trigger];
    [[UNUserNotificationCenter currentNotificationCenter] addNotificationRequest:request withCompletionHandler:nil];
}

---

提示：您的工作时间是24小时制，而不是12小时制。请阅读日期格式化程序规范。

@implementation ViewController {
    NSDateFormatter *parser;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    parser = [[NSDateFormatter alloc] init];
    parser.dateFormat = @"HH:mm:ss";
    parser.calendar = [NSCalendar autoupdatingCurrentCalendar];
}

- (void)createRepeatingNotificationAtTimeOfDay:(NSString *)timeOfDay {
    NSDate *date = [parser dateFromString:timeOfDay];
    if (date == nil) {
        // Couldn't parse the string.
        return;
    }

    NSDateComponents *components = [parser.calendar components:NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond fromDate:date];
    if (components == nil) {
        // Couldn't extract components.
        return;
    }

    UNCalendarNotificationTrigger *trigger = [UNCalendarNotificationTrigger triggerWithDateMatchingComponents:components repeats:YES];
    UNMutableNotificationContent *content = [[UNMutableNotificationContent alloc] init];
    content.title = @"Daily alarm";
    UNNotificationRequest *request = [UNNotificationRequest requestWithIdentifier:@"dailyalarm" content:content trigger:trigger];
    [[UNUserNotificationCenter currentNotificationCenter] addNotificationRequest:request withCompletionHandler:nil];
}