如何修改DateTimeImmuable？

Question

我在使用Symfony的项目中使用DateTimeImmutable时遇到了问题。我想在不改变第一次约会的情况下给一个日期加21天。但我有个错误：

DateTimeImmutable::__construct(): Argument #1 ($datetime) must be of type string, DateTime given

我试图将dateTime更改为string (我的尝试在下面代码中的注释中)。

// My class Borrowing

namespace App\Entity;

use App\Entity\User;
use App\Entity\BorrowingDetails;
use Doctrine\ORM\Mapping as ORM;
use App\Repository\BorrowingRepository;
use Doctrine\Common\Collections\Collection;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * @ORM\Entity(repositoryClass=BorrowingRepository::class)
 */
class Borrowing
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\Column(type="datetime")
     */
    private $dateStartBorrowing;

    /**
     * @ORM\Column(type="datetime")
     */
    private $dateLimitReturn;


    public function getId(): ?int
    {
        return $this->id;
    }

    public function getDateStartBorrowing(): ?\DateTimeInterface
    {
        return $this->dateStartBorrowing;
    }

    public function setDateStartBorrowing(\DateTimeInterface $dateStartBorrowing): self
    {
        $this->dateStartBorrowing = $dateStartBorrowing;

        return $this;
    }

    /**
     * @return Collection|BorrowingDetails[]
     */
    public function getBorrowingDetails(): Collection
    {
        return $this->borrowingDetails;
    }

    public function addBorrowingDetail(BorrowingDetails $borrowingDetail): self
    {
        if (!$this->borrowingDetails->contains($borrowingDetail)) {
            $this->borrowingDetails[] = $borrowingDetail;
            $borrowingDetail->setMyBorrowing($this);
        }

        return $this;
    }

    public function getDateLimitReturn(): ?\DateTimeInterface
    {
        return $this->dateLimitReturn;
    }

    public function setDateLimitReturn(\DateTimeInterface $dateLimitReturn): self
    {
        $this->dateStartBorrowing = $dateLimitReturn;

        return $this;
    }

    // I tried to add this function
    // public function __toString() {
    //     return $this->getDateStartBorrowing();
    // }
}

// This is my BorrowingController

$dateStartBorrowing = new \DateTime();
// I Tried : $dateStartBorrowing->format('Y-m-d H:i:s');

$dateLimitReturn = new \DateTimeImmutable($dateStartBorrowing);
$dateLimitReturn->modify('+21 days');
$dateLimitReturn->format('Y-m-d H:i:s');
            
$borrowing = new Borrowing();
$borrowing->setDateStartBorrowing($dateStartBorrowing);
$borrowing->setDateLimitReturn($dateLimitReturn);    

有人有答案吗？

如果我设法将其转换为字符串，那么我的其余代码是否会工作，因为在我的数据库中，它必须是一个日期时间吗？

Answer 1

\DateTimeImmutable不修改原始对象，而是为您提供一个新对象。

$today = new \DateTimeImmutable('now');
$inTenDays = $today->modify('+10 days'); 
dump($today); // is still 'now'
dump($inTenDays); // 10 days in future

因此有两种选择：

1. 存储在一个新变量
2. 中更改--在这个特殊情况下不要使用\DateTimeImmutable --

1)

$dateStartBorrowing = new \DateTime(); // which is now

$dateLimitReturn = \DateTimeImmutable::createFromMutable($dateStartBorrowing); // now it's an instance of DateTimeImmutable 
$modified = $dateLimitReturn->modify('+21 days');
...
$borrowing->setDateLimitReturn($modified);

For2)

$dateLimitReturn = clone $dateStartBorrowing; // you need a copy so you can modify $dateLimitReturn whithout changing the $dateStartBorrowing
$dateLimitReturn->modify('+21 days'); // $dateLimitReturn is now modified and 21 days in future
...
$borrowing->setDateLimitReturn($dateLimitReturn);

你也可以做得更短..。

$inTwentyOneDays = new \DateTimeImmutable('now + 21 days');
$borrowing->setDateLimitReturn($inTwentyOneDays);

更新：

TBH，我不知道您的业务逻辑，但在本例中，我看不到在常规\DateTime中使用\DateTimeImmutable的任何好处。

为什么？

由于实体的属性声明是：@ORM\Column(type="datetime") (从数据库读取后)，所以所有$ entity ->getDateLimitRe转折点()都是常规\DateTime anyway...unless，您有一些自定义原则类型