DEV Community: Othmane Nemli

Laravel WhereHas() and With()

Othmane Nemli — Tue, 06 Jul 2021 09:44:58 +0000

Quick recall:

When accessing Eloquent relationships as properties, the related models are "lazy loaded". This means the relationship data is not actually loaded until you first access the property. However, Eloquent can "eager load" relationships at the time you query the parent model. Eager loading alleviates the "N+1" query problem. To illustrate the *N+1 *query problem, consider a Book model that "belongs to" to an Author model:

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Book extends Model
{
 /**
 * Get the author that wrote the book.
 */
 public function author()
 {
 return $this->belongsTo(Author::class);
 }
}

We can use eager loading to reduce this operation to just two queries. When building a query, you may specify which relationships should be eager loaded using the with() method:

$books = Book::with('author')->get();
foreach ($books as $book) {
 echo $book->author->name;
}

Query Results:

select * from books
select * from authors where id in (1, 2, 3, 4, 5, …)

When retrieving model records, you may wish to limit your results based on the existence of a relationship. For example, imagine you want to retrieve all authors that have books' titles start with PHP. To do so, you may pass the name of the relationship to the whereHas() method and define additional query constraints on your has queries

$authors = Author::whereHas('books', function (Builder $query) {
 $query->where('title', 'like', 'PHP%');
})->get();

Query Result:

select * from authors WHERE EXISTS(SELECT * FROM authors WHERE authors.id = books.author_id and books.title like 'PHP%');

When this query gets executed you get all authors who have at least one book start with PHP, correct? Yes.
Now If you loop over the authors and access the book relationship like so,

foreach ($authors as $author) {
 echo $author->book->title;
}

You will end up with N+1, and to solve it sure you will use with() method to eager load books:

$authors = Author::with('books')
 ->whereHas('books', function (Builder $query) {
 $query->where('title', 'like', 'PHP%');
 })
 ->get();

Query Result:

select * from authors WHERE EXISTS(SELECT * FROM authors WHERE authors.id = books.author_id and books.title like 'PHP%');
select * from books where `books`.`author_id` in (1, 5, 11, 22, 46, 62, ….)

So far so good, we solve N+1 issue, but WAIT did you notice something, well I do, the 2nd query gets all books from only the authors that selected from the 1st query, right? Yes.
Our first query did its job and gets us only authors that have books that start with PHP, but the 2nd query (eager load) will get us all books for each author, that means if I looped over the authors and call book relationship we will see also other books not only those start with PHP.

[
 App\Author : {
 id: 1
 name: "author 1",
 …,
 books: [
 App\Books: {
 ….
 title: 'PHP'
 },
 App\Books: {
 ….
 title: 'Java'
 },
 App\Books: {
 ….
 title: 'How to use'
 },
 …
 ]
 }
 …
]

to get same results as we wanted from whereHas we need to use same condition query inside with() method.

$authors = Author::with(['books' => fn($query) => $query->where('title', 'like', 'PHP%')])
 ->whereHas('books', fn ($query) => 
 $query->where('title', 'like', 'PHP%')
 )
 ->get();

Query Results:

select * from authors WHERE EXISTS(SELECT * FROM authors WHERE authors.id = books.author_id and books.title like 'PHP%');
select * from books where `books`.`author_id` in (1, 5, 11, 22, 25, 27, 35, 39, 46, 62, ….) and books.title like 'PHP%');

I think you have already noticed the 2nd query has the same condition as 1st query.
Now, these are the results that we are looking for become:

[
 App\Author : {
 id: 1
 name: "author 1",
 …,
 books: [
 App\Books: {
 ….
 title: 'PHP'
 },
 …
 ]
 },
 App\Author : {
 id: 2
 name: "author 2",
 …,
 books: [
 App\Books: {
 ….
 title: 'PHP'
 },
 App\Books: {
 ….
 title: 'PHP Laravel'
 },
 …
 ]
 }
 …
]

- - - - - -
Finally, doing this query over all places and repeating the same conditions, is cumbersome, so we will use a local scope in Author model

public function scopeWithWhereHas($query, $relation, $constraint){
 return $query->whereHas($relation, $constraint)
 ->with([$relation => $constraint]);
}

Now, our code is much cleaner by calling it this way:

Author::withWhereHas('books', fn($query) =>
 $query->where('title', 'like', 'PHP%')
)->get();

Query Results:

select * from authors WHERE EXISTS(SELECT * FROM authors WHERE authors.id = books.author_id and books.title like 'PHP%');
select * from books where `books`.`author_id` in (1, 5, 11, 22, 25, 27, 35, 39, 46, 62, ….) and books.title like 'PHP%');

Since this query builder may be needed in many Models we will create a macro for it so all Models will have that scope, all you need is to add this snippet under *AppServiceProvider::boot() *

use Illuminate\Database\Eloquent\Builder;

Builder::macro('withWhereHas', fn($relation, $constraint) =>
 $this->whereHas($relation, $constraint)->with([$relation => $constraint]);
);

Well, you reach the end of this topic, I hope all is clear and if you have any similar thoughts or ideas, I would be happy if you share them with us.
Thank you

Different ways to use Laravel Form Requests

Othmane Nemli — Tue, 29 Jun 2021 11:25:18 +0000

Laravel provides several different approaches to validate your application’s incoming data. It is most common to use the validate method available on all incoming HTTP requests. However, in this topic, we will use Form Requests in different ways.

First of all, I don’t think using a small validation in the controller will harm your code readability but on the other hand, if you are willing to handle more complex validation scenarios, you may wish to create a “Form Request“.

Form requests are custom request classes that encapsulate their own validation and authorization logic.

Let’s create our own form request class, all you need is to run this command:

php artisan make:request StoreUserRequest

A new StoreUserRequest class will be generated under "\App\Http\Requests" namespace containing a rules() & authorize() methods.
Let’s add some quick validation under rules() method

/**
 * Get the validation rules that apply to the request.
 *
 * @return array
 */
public function rules()
{
    return [
        'name' => 'required|min:3|max:50',
        'email' => 'required|email|unique:users',
        'password' => 'required|confirmed|min:8',
        //... more validation
    ];
}

After that, we will inject our new Form request in the controller store() method

/**
 * Store a new user.
 *
 * @param  \App\Http\Requests\StoreUserRequest  $request
 * @return Illuminate\Http\Response
 */
public function store(StoreUserRequest $request)
{
    // The incoming request is valid...

    // Retrieve the validated input data...
    $validatedData = $request->validated();
}

So far so good, if the validation is valid we will get our validated data from Form request otherwise a Validation Exception will be thrown.

Now, what about the update, clearly we need to use another form request UpdateUserRequest with its rules and inject it in the controller update() method.

So this is the first and the simple approach used so far.

The second approach is using one class to handle the store and update rules, so, we will run the command again and create new Form Request by naming it UserRequest.

We create store() and update() functions and call them in rules() function by using isMethod() we're checking the HTTP request method if is it a POST or other than that, you may be specific and check if it is a PUT/PATCH.

As you may notice we can also share validations used in both methods and concatenate it with the proper validation function.

public function rules()
{
 return ['name' => 'required|min:3|max:50']
 +
 ($this->isMethod('POST') ? $this->store() : $this->update());
}

protected function store()
{
 return [
 'email' => 'required|email|unique:users',
 'password' => 'required|confirmed|min:8',
 //… more validation

 ];
}

protected function update()
{
 return [
 'email' => 'required|email|unique:users,email,'.$this->user()->id,
 'logo' => 'nullable|image|max:1024',
 'bio' => 'nullable|max:300',
 'github_url' => 'nullable|url'
 //… more validation

 ];
}

After that, we will inject UserRequest in both store() and update() methods.
Now, we have one class that serve different validation depends on HTTP request.

/**
 * Store a new user.
 */
public function store(UserRequest $request)
{
 $validated = $request->validated();
}
/**
 * Update user.
 */
public function update(UserRequest $request)
{
 $validated = $request->validated();
}

I will name the third approach “ResourceFormRequest” and it will be a little bit different from the others.

First I’ll create a BaseFormRequest that contains all resourceful methods, feel free to use your own naming just be careful when you name your methods to not end up overriding Request class methods.

After that, create UserRequest and extends BaseFormRequest, and override existing methods with your rules, finally inject the UserRequest inside your controller methods.

Our Resource Form Request can handle now a Controller resource and you end up with one file that manage all validations of specific Model instead of separate files which personally I don't like it.

I think there's a lot of approaches that we can follow and feel free to share your best approach or other approaches you have.

Finally, if you are reading this line I think the topic was interesting for you.

Thank you