Eloquent casting attributes to Collections unexpected behaviour - laravel

Question

Q1. I have an Eloquent model that casts an attribute to a Collection.
Calling Collection's method on this attribute doesn't affect the model values. Eg: put()
When using Collections , iam able to do this :
$var = collect();
$var->put('ip', '127.0.0.1');
var_dump($var);
Output as expected :
object(Illuminate\Support\Collection)[191]
protected 'items' =>
array (size=1)
'ip' => string '127.0.0.1' (length=4)
But when i use with a casted attribute on a Eloquent model, this doesn't work as expected
$user = App\User::create(['email'=>'Name', 'email'=>'mail#example.com', 'password'=>bcrypt('1234')]);
$user->properties = collect();
$user->properties->put('ip', '127.0.0.1');
var_dump($user->properties);
object(Illuminate\Support\Collection)[201]
protected 'items' =>
array (size=0)
empty
This doesn't populate the field.
I think that another collection is created, so to work as expected i must assign this new collection to my field.
Like so :
$user->properties = $user->properties->put('ip', '127.0.0.1');
Q2. Is there a proper way to initialize collection of the field by default (create an empty collection if the field is null), without having to call $user->properties = collect(); "manually" every time?
User.php
class User extends Authenticatable
{
protected $casts = [
'properties' => 'collection',
];
...
}
Migration file
Schema::table('users', function($table) {
$table->text('properties')->nullable();
});

Answer 1

Q1: an attribute casted to collection has a getter that returns, each time, a new BaseCollection that is constructed on the value of the attribute.
As already supposed the getter returns another collection instance and every direct change on it does not change the value of the attribute but instead the newly created collection object.
As also pointed by you the only way to set a a collection casted attribute is to assign it his own original value merged with new ones.
So instead of put() you have to use:
$user->properties = $user->properties->put('ip', '127.0.0.1');
// or
$user->properties = $user->properties ->merge(['ip'=>'127.0.0.1'])
Q2: We have to think that the database representation is a text; so IMHO the proper way to initialize a Model in the migration is to give it a default empty json, i.e.:
$table->text('properties')->default('{}');
But this works only for models created without setting the property field and retrieved after.
For a newly created Model my advice is to pass a default void array, i.e.:
App\User::create([
'name'=>'Name',
'email'=>'mail#example.com',
'password'=>bcrypt('1234'),
'properties' => []
]);

Answer 2

In addition to dparoli's outstanding answer, it is also possible to add a default value through Laravel's boot method, which is available on every Model.
Something like the following example code
protected static function boot()
{
parent::boot(); //because we want the parent boot to be run as well
static::creating(function($model){
$model->propertyName = 'propertyValue';
});
}
You can play with this approach if you like as well.