How to constraint scope of hasMany relationship in a query in Laravel - php

Question

I am working on a laravel based project comprising of Authors, Posts and Comments as models.
The relationship between the models is as follows:
Author -> hasMany Post
Post -> hasMany Comment.
The problem is as follows:
Authors made multiple posts, and all of them have multiple comments. I want to get the count of the Authors with comments from internal members only on their latest post.
My Models are shown below-
Author.php
public function post() {
return $this->hasMany('App\Post');
}
public function latestPost() {
return $this->hasOne('App\Post', 'latest_post_id', 'id')-
>orderBy('created_at', 'desc');
}
Post.php
public function comment() {
return $this->hasMany('App\Comment', 'post_id', 'id');
}
The query I am using to get the data are as follow:
$author_count = Author::whereHas('latestPost.comment', function ($query) {
$query->createdByInternal();
})->count();
When I execute this query, it considers all the Post models instead of only the latest Post and gives the authors who have a comment by an Internal member on any of their post.
However, on eager loading the latestPost query using "with" function, I get only the comments on the latest post.
$author = Author::with('latestPost.comment')->get();
Thanks in advance.

Answer 1

If you want to count authors who have posts with no created_by_internal
= null comments, use whereDoesntHave():
Author::whereDoesntHave('latestPost.comment', function ($query) {
$query->notCreatedByInternal();
})
->count();
In the relationship definition put foreign key before the id:
public function latestPost()
{
return $this->hasOne('App\Post', 'latest_post_id', 'id')->latest();
}
Also, change to scope to:
public scopeNotCreatedByInternal($query)
{
return $query->whereNull('created_by_internal');
}