对 Laravel model 关系插入应用一些约束

Question

I tried to find some suggestions in the web, but I couldn't...

I would like to use some constraints in the save method for a relationship in Laravel, I'll do an example to explain it

Let's suppose I've the 2 models Post and Comment , like in the Laravel documentation:

class Post extends Model
{
    public function comments()
    {
        return $this->hasMany('App\Comment');
    }
}

and

class Comment extends Model
{
    public function post()
    {
        return $this->belongsTo('App\Post');
    }
}

Now, I would like to do a check on a new comment inserting, for example I would like to avoid the insertion if more than ten comments for that post already exist.

I insert a new comment with these instructions

$comment = new Comment();
$post->comments()->save($comment);

I could check before these lines, but I would like to check in some other point, where all the saves are detected, is there something similar? Otherwise, is there some "standard way" to do it?

Answer 1

There are helper methods in eloquent Model class that are exactly what you need. Since you need to do the check before inserting, you want to use the static::creating or static::saving method. Use saving if you want to validate both when creating and updating a comment. In the Comment model add this:

protected static function boot()
{
    parent::boot();

    static::creating(function (Comment $comment) {
        // Do validation on the $comment model.
        // Feel free to make sql queries or do anything you need.
        // Throw an exception if your validation fails.
    });
}

Answer 2

You can do it with count(). Like beliw you can try. Where if the rows have less than 10 comments then it will save otherwise it will return back to the url.

$comment = new Comment();
If(count ($post->comments) <10){
$post->comments()->save($comment);
} 
else 
return back() ;//dont save return back;

Hope it will help