1452无法添加或更新子行：外键约束失败

Question

I get this error when creating a new product. This is the function:

public function createProduct(Request $request) {
    $product = Product::create($request->all());
    $product->title = strip_tags($request->title);
    $product->description = strip_tags($request->description);
    $product->price = strip_tags($request->price);

    $product->category_id = 1;
    $product->save();
    return redirect('/');
}

'insert into products ( title , description , price , image , updated_at , created_at ) values (?, ?, ?, ?, ?, ?)

But why I can't see category_id between these values ? I also made category_id fillable in Product.php

protected $fillable = [
    'slug', 'title', 'description', 'stock', 'price', 'image',
    'category_id'
];

And I've also created category in categories table with an ID of 1

Can someone help ?

Answer 1

Your problem is you create and save the model before you set the category_id. Your request data must not have a category ID.

$product = Product::create($request->all());

This will attempt to insert the row (create+save the model) into the database using the data you pass to it.

So by the time you hit:

$product->title = strip_tags($request->title);

Your insert query has already been sent. For readability sake, don't mix create or make with setters. Either do:

$product = Product::create([
   'category_id' => 1,
   ...
]);

Or do:

$product = new Product();
$product->category_id = 1;
...
$product->save();