How to let Laravel pivot table use only created_at? - php

Question

When dealing with belongsToMany relation, you use a pivot table to record the relation.
For many pivot tables, the relations are just created and then deleted. They won't have their own property, so you never update them.
I know I can do this to auto-set both updated_at and created_at.
class Foo extends Model
{
public function bars() {
$this->belongsToMany(Bar::class)->withTimestamps();
}
}
But how to use only created_at? I have no idea.

Answer 1

You could take another approach:
Skip the withTimestamps() method (to avoid adding both created_at and updated_at columns).
Add a custom pivot column: created_at.
So your code:
class Foo extends Model
{
public function bars() {
$this->belongsToMany(Bar::class)->withPivot('created_at');
} // ^^^^^^^^^^^^^^^^^^^^^^^^
}
Now, with this approach you will need to set the value of created_at manually when creating records:
$foo = Foo::find(1);
$foo->bars()->attach($someId, ['created_at' => now()->format('d-m-Y H:i:s')]);
// or whatever you use as date ^^^^^^^^^^^^^
Also, this column won't be casted as a Date by default -as opposed to what Laravel do with timestamp columns- so this:
$foo->bars()->first()->pivot->created_at
won't be an instance of Carbon. If you want it though, you could create a custom Pivot model, then specify the column to cast and update your relationship to use the custom Pivot model:
Pivot model FooBar.php
class FooBar extends Pivot // <--
{
protected $casts = [
'created_at' => 'datetime:d-m-Y H:i:s',
];
}
Then in your Foo.php class:
class Foo extends Model
{
public function bars() {
$this->belongsToMany(Bar::class)->using(FooBar::class)->withPivot('created_at');
// ^^^^^^^^^^^^^^^^^^^^
}
}