如何在Laravel 5中为模型中的现有字段定义访问器？

Question

I have a model called Book for a table called books, that has a field called cover_image.

However, I want to define an accessor for the field cover_image instead of just retrieving the default value.

This is how I attempted to do this:

class Book extends Model {

    public function getCoverImageAttribute() {

         if ($this->cover_image === null) { // Not sure how to check current value?
               return "a.jpg"
         }
         return $this->cover_image; 
    } 

}

However the above of course does not work because calling $this->cover_image again would cause recursion

How can I fix this?

Answer 1

You must check for the attribute instead:

class Book extends Model {

    public function getCoverImageAttribute() {
         return $this->attributes['cover_image'] ?? "a.jpg"; 
    } 

}

This will allow you to normally use $book->cover_image as well.

I believe the following example will also work:

class Book extends Model {

    public function getCoverImageAttribute($value) {    

         return is_null($value) ? 'a.jpg' : $value; 
    } 

}