Return Eloquent Relationship Dependent on Value of Field in Model

Question

Say I have a Model, and I want to return a relationship, but it depends on a value of an attribute of the model. I tried this in my model:

public function paymentType(){
    if($this->type > 1) return $this->hasOne(PaymentType::class, 'type', 'type');
    if($this->type == 1) return $this->hasOne(PaymentType::class, 'payment_type', 'pay_type');
}

When I have an instance of the model, I can call this relationship fine, however when I try to eager load, and call with('paymentType'), I get the exception Call to a member function addEagerConstraints() on null

Answer 1

I would imagine that your issue with eager loading arises because the models are not yet populated with values. Trying to check for a model's type with $this->type goes against the nature of eager loading.

You options are to:

A) Use lazy loading so that type is populated in the model before you call the relationship, or

B) Use eager loading constraints