How to get 5 latest post for each genre Laravel API? - php

Question

I'm building an application (my course project) with Laravel 5.4 as API and Angular 5. My project is a music blog. I need to fulfill requirements such as to have categories and subcategories.
So, I have genres, bands and posts. For my home page I want to display 5 latest posts for each category.
My tables
genres(id, name, slug);
bands(id, name, slug, genre_id);
posts(id, title, content, band_id, slug, created_at, updated_at).
My relationships
Genre.php
protected $fillable = ['name', 'slug'];
public function bands()
{
return $this->hasMany('App\Models\Band');
}
public function posts()
{
return $this->hasManyThrough('App\Models\Post', 'App\Models\Band');
}
Band.php
protected $fillable = ['name','slug','genre_id'];
public function genre()
{
return $this->belongsTo('App\Models\Genre');
}
public function posts()
{
return $this->hasMany('App\Models\Post');
}
Post.php
protected $fillable = ['title','content','image','band_id','slug'];
public function band()
{
return $this->belongsTo('App\Models\Band');
}
In my HomeController I've tried:
$latest5PostsPerGenre = Genre::with([
'posts' => function($query) {
$query->take(5)
->orderBy('id', 'desc')
->get(['posts.id', 'title']);
}])->orderBy('name')
->get();
But it limits the total number of posts to 5 I got for all genres. So, some genres don't have posts at all.
$latest5PostsPerGenre = Genre::with('latest5Posts')
->orderBy('name')
->get();
with such methods in Genre model:
public function latest5Posts()
{
return $this->hasManyThrough('App\Models\Post', 'App\Models\Band')
->orderBy('id', 'desc')
->take(5)
->get();
}
or
public function latest5Posts()
{
return $this->posts()->latest()->take(5)->get();
}
But I got BadMethodCallException Method addEagerConstraints does not exist.
I even tried something like this:
$genres = Genre::with('posts')->orderBy('name')->get();
$latest5PostsPerGenre = [];
foreach ($genres as $genre) {
$genrePosts['posts'] = [];
$posts = $genre->posts()->orderBy('id', 'desc')->take(5)->get();
foreach ($posts as $post) {
$singePost = [];
$singePost['id'] = $post->id;
$singePost['title'] = $post->title;
$singePost['bandName'] = $post->band->name;
array_push($genrePosts['posts'], $singePost);
}
array_push($latest5PostsPerGenre[$genre->name], $genrePosts);
}
or like this
$genres = Genre::get();
foreach ($genres as $genre) {
$post[$genre->name] = $genre->posts()
->take(5)
->orderBy('id', 'desc')
->get();
}
But I understand it performs a lot of queries to db and is not right.
I tried to create method scopeNPerGroup in Model.php according to the link https://softonsofa.com/tweaking-eloquent-relations-how-to-get-n-related-models-per-parent/, but it gives be a bunch of sql errors.
I was thinking about some complex, nested sql query with Eloquent, but don't clearly understand how to write it.
As a result, I'm expecting to have each genre name with 5 latest posts containing id, title and band name for each post in order to write the link for each post in my Angular frontend like rnmblog.com/api/{genre-slug}/{band-slug}/{post-id} or {post-slug} to get single post.

Answer 1

For my home page I want to display 5 latest posts for each category.
Your first attempt already does this, isn't it? Just improved it a bit
$latest5PostsPerGenre = Genre::with([
'posts' => function($query) {
$query->with('bands')
->take(5)
->orderBy('id', 'desc')
->get();
}])
->orderBy('name')
->get();