laravel 多对多关系新

Question

i am facing a problem. i am new in laravel. i created many to many relation in my application.but it's shown error. please check bellow code:

Error

SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'post_id' cannot be null (SQL: insert into `category_post` (`category_id`, `created_at`, `post_id`, `updated_at`) values (1, 2019-11-09 17:00:29, ?, 2019-11-09 17:00:29))

Post Model code:

public function  categories()
{
    return $this->belongsToMany('App\Category')->withTimestamps();
}

Category model code

public function posts()
{
    return $this->belongsToMany('App\Post')->withTimestamps();
}

PostController Code

 public function store(Request $request)
{
    $this->validate($request,[


    ]);

    $image = $request->file('image');
    $slug = str_slug($request->name);

    if(isset($image))
    {
        $imageName = $slug.'-'.time().uniqid().'.'.$image->getClientOriginalExtension();

        if(!Storage::disk('public')->exists('posts/'))
        {
            Storage::disk('public')->makeDirectory('posts/');
        }
        $postImage = Image::make($image)->resize(1600,1066)->stream();

        Storage::disk('public')->put('posts/'.$imageName,$postImage);
    }else{

        $imageName = 'default.png';
    }



    $posts = new Post();

    $posts->user_id =Auth::id();

    $posts->title = $request->title;
    $posts->slug = $slug;
    $posts->body = $request->body;
    $posts->image = $imageName;

    $posts->categories()->attach($request->categories);
    $posts->tags()->attach($request->tags);

    $posts->is_approved = true;
    if(isset($request->status))
    {
        $posts->status = true;
    }else{

        $posts->status = false;
    }



    $posts->save();

  //  $posts->tags()->attach($request->tags);
    Toastr::success('Post Is created successfully','Success');
    return redirect()->route('admin.posts.index');

}

My create.blde.php file code is okey all request goes appropriately but above error shown when i submit my post..Thank in advance

Answer 1

You have a belongs to many relationship between posts and categories . In order to create that relationship on your pivot table, you must have a category_id and a post_id .

This line in your code:

 $posts->categories()->attach($request->categories);

is correct, but you are trying to attach the categories to the post object before you have saved it. Thus, the unsaved post object has no id yet.

Save your post , and then attach the categories with the attach() method you have already written.

Same thing with your tags() attachment. Stick it in after you have saved the post object.

Answer 2

Save the post model object before you attach other models

$posts = new Post();

$posts->user_id = auth()->id();
$posts->title = $request->title;
$posts->slug = $slug;
$posts->body = $request->body;
$posts->image = $imageName;
$posts->is_approved = true;
$posts->status = $request->status ? true : false;

$posts->save();

$posts->categories()->attach($request->categories);
$posts->tags()->attach($request->tags);

Hope this helps