如何在同一个controller函数中创建Model后，马上检索到Model的id？

让我给你看看我的代码，并放上注释，让你们更好的理解。

$homework = new Homework([ // I create Homework (And I indeed want to get the ID of the one that was just created).
    'subject_id' => $request->subject_id,
    'user_id' => auth()->user()->id,
    'title' => $request->name,
    'image' => $path,
    'progress' => $request->progress,
    'description' => $request->description,
    'duedate' => $request->date
]);

$homework->save(); // I save it

$homeworkid = Homework::where('id', $id)->first(); // I try to retrieve it, but I'm not sure how to get it as I need to define `$id`.

$progress = newProgress([
    'user_id' => auth()->user()->id,
    'homework_id' => $homeworkid, // I need this for the relationship to work.
    'title' => 'Initial Progress',
    'description' => 'This progress is auto-generated when you create an assignment',
    'username' => auth()->user()->name,
    'progress' => $homeworkid->progress
]);

$progress->save(); // I save the progress

正如你们所看到的，我正在尝试检索一个模型的ID Homework 但我不知道该如何定义 $id 以便获取它。

解决方案：

如果你在实例化和保存之间没有做任何事情，就没有必要实例化一个新的模型并保存它，你可以使用 create 方法来代替。

$homework = Homework::create([
    'subject_id' => $request->subject_id,
    'user_id' => auth()->user()->id,
    'title' => $request->name,
    'image' => $path,
    'progress' => $request->progress,
    'description' => $request->description,
    'duedate' => $request->date
]);

$homework->id; // get the id

保存创建模型后，你可以访问 id 就像你平时一样。

$homework->id

然后你可以做的是设置 关系 在你的模型之间，所以你可以在创建一个新的作业后，进行以下操作。

$homework->newProgress()->create([
    'user_id' => auth()->user()->id,
    'title' => 'Initial Progress',
    'description' => 'This progress is auto-generated when you create an assignment',
    'username' => auth()->user()->name,
    'progress' => $homework->progress
]);

这样一来，你就不用再通过作业了 id 当创建一个新的 newProgress，laravel会自动为你传递。