sole relationship modifier

[shaedrich]

There's already Relation::sole(), but it isn't a modifier but executes the query, so it can't be used with with(), for example.

Let's assume, we have a process with multiple steps. Within the first step, a relationship might return null, but will be set by the end of said step.

class ChildModel
{
    public function parent(): HasOne
    {
        return $this->hasOne(ParentModel::class);
    }
}

In the subsequent steps, I want to eager load said model but there might be cases, where we get an exception like this:

Caution

Attempt to read property "name" on null

If I don't want to check this manually, maybe even in several separate places and don't want an accessor in the model, I can have a separate relationship:

class ChildModel
{
    // parent relationship

    public function mandatoryParent()
    {
        return $this->parent()->withDefault(fn (Model $relation) => throw (new ModelNotFoundException)->setModel($relation::class));
    }
}

This works, however, it would be even nicer, if there was an out-of-the-box modifier to achive this without manually instanciating the exception and setting the model like with sole().

[ghost]

I guess you are mentioning this because you are using the relation with magic call like
$child->parent->name
What is wrong with
$child->parent?->name
?

[shaedrich]

I do. Sometimes, you want null, but sometimes, you want an exception because neither parent nor parent.name can be null

[ghost]

\Illuminate\Database\Eloquent\Concerns\HasAttributes::getRelationValue

/**
* Get a relationship.
*
* @param string $key
* @return mixed
*/
public function getRelationValue($key)
{
// If the key already exists in the relationships array, it just means the
// relationship has already been loaded, so we'll just return it out of
// here because there is no need to query within the relations twice.
if ($this->relationLoaded($key)) {
return $this->relations[$key];
}

You can overwrite this method as

$parent = parent::...'

if ($parent === null) { // is this null also for one to many relation?
 throw
} 
  return $parent;

in your model

[shaedrich]

as I said:

[…] I don't want to check this manually, maybe even in several separate places and don't want an accessor in the model […] [but] a separate relationship.