Eager load extra model attributes - php

I am using Eloquent with Laravel.
The case: I'm building an API where there is possibility to include relations for a Resource. So for example /api/teams?include=users will add the User model for every Team. For the logic that includes the relationship I'm using Fractal. So I need to have some logic that determines which relationship has to be included, so I can create a optimized query for it.
Problem: When I want to render a collection of a Team with the related User models. I can eager-load the models just fine. The problems comes when I have custom attributes on the User model. These will cause a N+1 query problem because for every eager-loaded team, because the query for the custom attributes will be executed for every model.
Example code:
// The Team model with the custom attribute
class Team extends Model {
protected $appends = ['is_member'];
public function getIsMemberAttribute() {
$loggedUser = Auth::currentUser();
$result = DB::table('team_user')
->where('team_id', $this-id)
->where('user_id', $loggedUser->id)
->get();
return !is_null($result);
}
}
// The controller code
$team = Team::findOrFail($teamId);
// So this will return all the User models that belong to the Team.
// The problem is this will execute the query inside the getIsMemberAttribute() for every User model.
dd($team->users);
Is there a good pattern to solve this issue?

You could iterate through the User models and see if one of them matches the logged in user. It's more efficient than looking it up in the database.
class Team extends Model {
protected $appends = ['is_member'];
public function getIsMemberAttribute() {
$loggedUser = Auth::currentUser();
foreach ($this->users as $user) {
if ($user->id == $loggedUser->id) {
return true;
}
}
return false;
}
}

Related

Using eloquent relation

I am trying to understand how to effectively use Eloquent relationships to have some high level functions in the model.
I have a subscription app with 2 tables, 'users' and 'subscriptions'.
This is a legacy system so I cannot just change things in any way I want.
Table users (model App\User)
id
email
active (0/1)
join_date
address etc
phone
Table subscriptions (model App\Subscription)
id
user_id
box_id (what the person is subscribed to get)
amount
Users are marked active or not active.
I would like to have a static method on the Subscription model that will give me all the active subscriptions. This data is then fed into other parts of the application.
This is derived by joining subscriptions to users and filtering based on the active column.
The query is like this:
SELECT users.*, subscriptions.*
FROM subscriptions
JOIN users ON users.id = subscriptions.user_id
WHERE users.active = 1
Subscription model
class Subscription extends Model
{
public static function allActive()
{
// This works except it doesn't use the eloquent relationship
return static::where('users.active', 1)
->join('users', 'users.id', '=', 'subscriptions.user_id')
->select('users.*','subscriptions.*')
->get();
}
public function user()
{
return $this->belongsTo(User::class);
}
}
User model
class User extends Authenticatable
{
use Notifiable;
public function subscriptions()
{
return $this->hasMany(Subscription::class);
}
}
I would use it like this:
$subscriptions = \App\Subscription::allActive()->toArray();
print_r($subscriptions);
I have 2 questions.
How do I rewrite the allActive function to use the relationship I already defined? Any solution should generate SQL with a JOIN.
In the returned data, how do I separate the columns from the two separate tables so that it is clear which table the data came from?
Given the relationships you have wired up, to get only active subscriptions from the model class you will have to do it this way:
class Subscription extends Model
{
public static function allActive()
{
$activeSubcriptions = Subscription::whereHas('user', function($query){
$query->where('active', 1) //or you could use true in place of 1
})->get();
return $activeSubcriptions;
}
public function user()
{
return $this->belongsTo(User::class);
}
}
Thats working with closures in Laravel, quite an efficient way of writing advanced eloquent queries.
In the callback function you will do pretty much anything with the $query object, its basically working on the User model since you mentioned it as the first parameter of the ->whereHas
Note that that variable has to have EXACTLY the same name used in declaring the relationship
The above i suppose answers your first question, however its highly recommended that you do most of this logic in a controller file
To answer question 2, when you execute that get() it will return Subscription objects array so to access the info based on columns you will have to go like:
$subscriptions = \App\Subscription::allActive();
foreach($subscriptions as $subscription){
$amount = $subscription->amount; //this you access directly since we working with the subscription object
$box_id = $subscription->box_id;
//when accessing user columns
$email = $subscription->user->email; //you will have to access it via the relationship you created
$address = $subscription->user->address;
}

Why I can't retrieve data using a one-to-many relationship in laravel 5.5

I am trying to return data from my database and I want it to include data from the related table. It is a one-to-many relationship. However I all I get is an error
Property [User] does not exist on this collection instance.
In my User model I have
//App\User.php
class User extends Authenticatable{
use Notifiable;
public function systems(){
return $this->hasMany(\App\Models\General\systems::class,'added_by','id');
}
The other model, called systems I have
//App\Models\General\systems.php
class systems extends Model
{
public function User(){
return $this->belongsTo(\App\User::class,'added_by','id');
}
In my controller I have
$this->systemsObject = new \App\Model\General\systems();
$systems = $this->systemsObject->get()->User;
according to the Laravel Documentation this should work but it isn't. I tried reversing the foreign key/local key parameters. I made the ->User uppercase, lowercase.
I have no idea what I am doing wrong
You need to iterate over the collection, for example:
$systems = $this->systemsObject->get();
foreach ($systems as $system) {
echo $system->User->name;
}

how to get a belongsToMany() query from a collection ? MySQL/Laravel

I'm using Laravel 5.4.22 (the newest one). In MySQL, I have two tables, tag_categories and tags, which form a many-to-many relationship. What I need is a query which returns all the tags for the selected categories. I know how to solve this when I have only one object, and I know how to solve this with querying and looping each of those objects, but there has to be a query or eloquent based solution for the whole thing?
I understand the code below doesn't work because I'm using ->belongsToMany on a collection rather than an object, but how to I bridge this gap the simplest way?
$resultingTags = TagCategory::whereIn('id', $chosenCategoriesIds)
->belongsToMany(Tag::Class)->get();
dd($resultingTags);
belongsToMany generally belongs in the model class, not a method called on the fly. When looking to eager load the relationship, you then call the with() method on the query builder.
https://laravel.com/docs/5.4/eloquent-relationships#many-to-many
ex:
class User extends Model
{
/**
* The roles that belong to the user.
*/
public function roles()
{
return $this->belongsToMany('App\Role');
}
}
// Query
$users = User::with('roles')->get();
$rolesOfFirstUser = $users->first()->roles;
If you're trying to get all the tags of the given categories, then you should be querying tags, not tag_categories.
Tag::whereHas('categories', function ($query) use ($chosenCategoriesIds) {
$query->whereIn('id', $chosenCategoriesIds);
})->get();
This is One-to-many relation
Define relation at TagCategory model at app/TagCategory.php
public function tags()
{
return $this->hasMany('App\Tag');
}
And handle at your Controller
$resultingTags = TagCategory::whereIn('id', $chosenCategoriesIds)->with(['tags'])->get();
If you want define Many-To-Many relation for this case
You need to have 3 tables tags, tag_categories, tag_tag_category
Define relation at TagCategory model at app/TagCategory.php
public function tags()
{
return $this->belongsToMany('App\Tag', 'tag_tag_category', 'tagcategory_id', 'tag_id');
}
And handle at your Controller
$resultingTags = TagCategory::whereIn('id', $chosenCategoriesIds)->with(['tags'])->get();

How to return one property of a belongsTo model with the child model in Laravel resource controller

I'm using Laravel as a REST API for a SPA. I have a relationship where families have multiple contributions. The contributions table has a foreign key reference to family's id. I can call on the contributions route with the hasMany/belongsTo set up, and every contribution gets the entire family model it belongs to. But I don't need all that data, I just need a single field from the family table (not the id, but a different field) with each contribution.
Here are my models and resource controller:
class Family extends Eloquent {
protected $table = 'families';
// relationships
public function contributions() {
return $this->hasMany('Contribution');
}
}
class Contribution extends Eloquent {
protected $table = 'contributions';
// relationships
public function family() {
return $this->belongsTo('Family');
}
public function other_field() {
return $this->belongsTo('Family')->select('other_field');
}
}
class ContributionController extends BaseController {
public function index()
{
// works - but returns the entire family with every contribution
$contributions = Contribution::with('family')->get();
// returns other_field == null with every contribution
$contributions = Contribution::with('other_field')->get();
return Response::json($contributions->toArray(),
200);
}
Where am I going wrong with selecting this single field from the belongsTo relationship?
You can use query constraints on the relationship if you use eager loading.
Family::with(['contributions', function($query)
{
$query->select('column');
}])->get();

Check for a many to many relation when listing a resource

I'm implementing relationships in Eloquent, and I'm facing the following problem:
An article can have many followers (users), and a user can follow many articles (by follow I mean, the users get notifications when a followed article is updated).
Defining such a relationship is easy:
class User extends Eloquent {
public function followedArticles()
{
return $this->belongsToMany('Article', 'article_followers');
}
}
also
class Article extends Eloquent {
public function followers()
{
return $this->belongsToMany('User', 'article_followers');
}
}
Now, when listing articles I want to show an extra information about each article: if the current user is or is not following it.
So for each article I would have:
article_id
title
content
etc.
is_following (extra field)
What I am doing now is this:
$articles = Article::with(array(
'followers' => function($query) use ($userId) {
$query->where('article_followers.user_id', '=', $userId);
}
)
);
This way I have an extra field for each article: 'followers` containing an array with a single user, if the user is following the article, or an empty array if he is not following it.
In my controller I can process this data to have the form I want, but I feel this kind of a hack.
I would love to have a simple is_following field with a boolean (whether the user following the article).
Is there a simple way of doing this?
One way of doing this would be to create an accessor for the custom field:
class Article extends Eloquent {
protected $appends = array('is_following');
public function followers()
{
return $this->belongsToMany('User', 'article_followers');
}
public function getIsFollowingAttribute() {
// Insert code here to determine if the
// current instance is related to the current user
}
}
What this will do is create a new field named 'is_following' which will automatically be added to the returned json object or model.
The code to determine whether or not the currently logged in user is following the article would depend upon your application.
Something like this should work:
return $this->followers()->contains($user->id);

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