Laravel 关系属性在此集合实例中不存在

Question

$category = Category::orderBy('category_name_en', 'ASC')
->get();

$subcategory = SubCategory::where('category_id', $category->id)
->orderBy('subcategory_name_en', 'ASC')
->get();

$subsubcategory = SubSubCategory::where('subcategory_id', $subcategory->id)
->orderBy('subsubcategory_name_en', 'ASC')
->get();

return view('welcome', compact('category', 'subcategory', 'subsubcategory'));

In this above code we are getting error:

Property [id] does not exist on this collection instance.

Why is this error showing?

Answer 1

That's because you are returning a Collection whenever you write get .

Try this instead:

$category = Category::orderBy('category_name_en', 'ASC')
->get();

$subcategory = SubCategory::whereIn('category_id', $category->pluck('id'))
->orderBy('subcategory_name_en', 'ASC')
->get();

$subsubcategory = SubSubCategory::whereIn('subcategory_id', $subcategory->pluck('id'))
->orderBy('subsubcategory_name_en', 'ASC')
->get();

return view('welcome', compact('category', 'subcategory', 'subsubcategory'));

The changes being where converted to whereIn , and ->id becomes ->pluck('id') .

As you can see from the documentation, whereIn accepts an array of values for it's second argument, and pluck will return an array of, in our case, IDs.
Combining these will mean that category_id will need to exist within the array.

---

If, however, these models were supposed to supply a single Model.
Then you should do the following:

$category = Category::orderBy('category_name_en', 'ASC')
->first();

$subcategory = SubCategory::where('category_id', $category->id)
->orderBy('subcategory_name_en', 'ASC')
->first();

$subsubcategory = SubSubCategory::where('subcategory_id', $subcategory->id)
->orderBy('subsubcategory_name_en', 'ASC')
->first();

return view('welcome', compact('category', 'subcategory', 'subsubcategory'));

This is using the first method to return a single instance.