laravel雄辩地用多个FK进行多对多连接

Question

I have four tables:

categories
id, name

products
id, name

files
id, location

category_product
id, cateogry_id, product_id, file_id

There are many to many relationships between product and category, as well as product and file. Both relationships are saved in the table category_product. I have also setup the appropriate models and would now like to create the associations:

$category = new Category();
$category->name = "Electronics";
$category->save();

$file = new File();
$file->location = "some\path";
$file->save();

$product = new Product();
$product->save()
$product->Categories()->attach($category);
$product->Files()->attach($file);

However, it complains that there is a FK violation. This is because the attach statements are processed sequentially and the first one will fail because it only sets the category relationship, while category and file are required at the same time.

Is it possible to use attach when there are multiple FKs?

Answer 1

Laravel documentation says you can give additional data to the attach method:

When attaching a relationship to a model, you may also pass an array of additional data to be inserted into the intermediate table:

$user->roles()->attach($roleId, ['expires' => $expires]);

https://laravel.com/docs/5.4/eloquent-relationships#many-to-many

In your case:

$product->Categories()->attach($category, ['file_id' => $file->id]);

But it seems strange to mix the two relations in one table.