如何向 Chrono NaiveDate 添加月份？

Question

我正在尝试创建一个日期选择器，我需要在几个月之间导航

let current = NaiveDate::parse_from_str("2020-10-15", "%Y-%m-%d").unwrap();

我怎样才能生成日期2020-11-15？

Answer 1

这是我的解决方案：

use chrono::{ NaiveDate, Duration, Datelike};

fn get_days_from_month(year: i32, month: u32) -> u32 {
    NaiveDate::from_ymd(
        match month {
            12 => year + 1,
            _ => year,
        },
        match month {
            12 => 1,
            _ => month + 1,
        },
        1,
    )
    .signed_duration_since(NaiveDate::from_ymd(year, month, 1))
    .num_days() as u32
}

fn add_months(date: NaiveDate, num_months: u32) -> NaiveDate {
    let mut month = date.month() + num_months;
    let year = date.year() + (month / 12) as i32;
    month = month % 12;
    let mut day = date.day();
    let max_days = get_days_from_month(year, month);
    day = if day > max_days { max_days } else { day };
    NaiveDate::from_ymd(year, month, day)
}

fn main() {
    let date = NaiveDate::parse_from_str("2020-10-31", "%Y-%m-%d").unwrap();
    let new_date = add_months(date, 4);
    println!("{:?}", new_date);
}

Answer 2

NaiveDate现在有一个方法checked_add_months

assert_eq!(
    NaiveDate::from_ymd(2020, 10, 15).checked_add_months(chrono::Months::new(1)),
    Some(NaiveDate::from_ymd(2020, 11, 15))
);
assert_eq!(
    NaiveDate::from_ymd(2020, 10, 15).checked_add_months(chrono::Months::new(3)),
    Some(NaiveDate::from_ymd(2021, 1, 15))
);