[11.x] Added for method to Eloquent models

[ash-jc-allen]

Hey!

This PR proposes a new for method that helps set foreign keys on models. It's a fresh (and simplified!) take on my past attempt from a couple of years ago: #42467

I think a major drawback of the previous approach was that it wasn't obvious whether for would be used in queries, or for setting fields on models. So it got a bit confusing!

In this approach, I've completely ditched the Builder side of things. Although on the surface, it looks like it would have been nice, I think it would have caused more issues than it solved! So, instead, the for method only exists on the Model classes.

So you can call it like so:

use App\Models\Comment;
use App\Models\Post;
use App\Models\User;

// Imagine these are from a request or something instead.
$post = Post::first(); // ID: 123
$user = User::first(); // ID: 456



// Before:
$comment = Comment::create([
    'comment' => 'hello',
    'post_id' => $post->id,
    'user_id' => $user->id,
]);



// After (using the "for" method):
$comment = Comment::make(['comment' => 'hello'])
    ->for($post)
    ->for($user);

$comment->save();

Assuming there is a posts and users relationship, the comment will now have the following data set:

'comment' => 'hello'
'post_id' => 123,
'user_id' => 456,

There's also the ability to specify the relationship name if needed:

Comment::make(['comment' => 'hello'])
    ->for($post, 'blogPost')
    ->for($user)
    ->save();

I also quite like how it almost reads like a human-readable sentence when it's written like this too:

new Comment()
    ->for($post)
    ->for($user)
    ->fill(['comment' => 'hello'])
    ->save();

Hopefully this is something that other devs would also find useful. Although it's a relatively small change, I like the way that it can reduce the likelihood of typos and also uses a similar syntax to model factories.

But I completely understand if it's not something worth merging in. I'd kick myself if I didn't try and scratch the itch though haha!

If it's something you might consider merging, please let me know if there's anything you might want me to change 😄

[Bosphoramus]

Yes, please! 🤩🤩

[caendesilva]

I love it. The implementation looks simple and easy to maintain, whilst the feature is very useful.

[osbre]

Wouldn't it be better if this was powered by actual relationship method assignments? So

$store->owner()->assign($user);

If I recall correctly

[ahinkle]

I can see the benefit, but it feels a bit ambiguous and might raise questions if I came across it while browsing the code—or for juniors who might struggle to decide which approach to use. The existing methods are a bit more explicit in their intent.

Cool idea though!