在 Laravel 测试中对 null 调用成员函数 save()

Question

到目前为止我有一个类别模型：

class Category extends Model

{   

    protected $fillable = [

        'name',

        'slug',

        'order'

    ];

    public function scopeParents(Builder $builder){

        $builder->whereNull('parent_id');

    }

    public function scopeOrder(Builder $builder, $direction = 'asc'){

        $builder->orderBy('order', $direction);

    }

    public function children(){

        $this->hasMany(Category::class, 'parent_id', 'id');

    }

}

一个工厂：

$factory->define(Category::class, function (Faker $faker) {

    return [

        'name' => $name = $faker->unique()->name,

        'slug' => Str::slug($name)

    ];

});

还有一个测试

public function test_it_has_many_children()

    {

        $category = factory(Category::class)->create();

        $category->children()->save(

            factory(Category::class)->create()

        );

        $this->assertInstanceOf(Category::class, $category->children->first());

    }

但是，当我运行测试时，我得到：

Call to a member function save() on null

  at tests/Unit/Models/Categories/CategoryTest.php:14

    10|     public function test_it_many_children()

    11|     {

    12|         $category = factory(Category::class)->create();

    13| 

  > 14|         $category->children()->save(

    15|             factory(Category::class)->create()

    16|         );

    17| 

    18|         $this->assertInstanceOf(Category::class, $category->children->first());

是什么赋予了？该课程已经有几年的历史了，所以我认为 Laravel 版本之间存在一些差异，但这似乎更基本。

Answer 1

您的关系方法中缺少返回：public function children(){     return $this->hasMany(Category::class, 'parent_id', 'id'); }