Multiple Components: Dispatching Events

There are a lot of cases where one Livewire component needs to communicate with another. In this lesson, let's see how it is done using Events.

Initial Components

In this example, we will have a Livewire component for showing a post and another component for posting a comment. When a comment is posted, the comment count in the ViewPost Livewire component should be updated.

DB structure: the Comment Model only has the post_id and body fields. And we need a comments() relationship in the Post Model.

database/migrations/xxxx_create_comments_table.php:

Schema::create('comments', function (Blueprint $table) {
    $table->id();
    $table->foreignId('post_id');
    $table->string('body');
    $table->timestamps();
});

app/Models/Post.php:

use Illuminate\Database\Eloquent\Relations\HasMany;
 
class Post extends Model
{
    protected $fillable = [
        'title',
        'body',
    ];
 
    public function comments(): HasMany 
    {
        return $this->hasMany(Comment::class);
    } 
}

And here is the initial Livewire components.

app/Livewire/ViewPost.php:

use App\Models\Post;
use Illuminate\Contracts\View\View;
 
class ViewPost extends Component
{
    public Post $post;
 
    public int $commentsCount = 0;
 
    public function mount(Post $post): void
    {
        $this->post = $post;
        $this->post->loadCount('comments');
        $this->commentsCount = $this->post->comments_count;
    }
 
    public function render(): View
    {
        return view('livewire.view-post');
    }
}

resources/views/livewire/view-post.php:

<div class="py-12">
    <div class="max-w-7xl mx-auto sm:px-6 lg:px-8">
        <div class="bg-white dark:bg-gray-800 overflow-hidden shadow-sm sm:rounded-lg">
            <div class="p-6 text-gray-900 dark:text-gray-100">
 
                <h1 class="text-lg font-bold mb-4">{{ $post->title }}</h1>
 
                <p>Comments: {{ $commentsCount }}</p>
 
                <livewire:create-comment :post="$post" />
            </div>
        </div>
    </div>
</div>

app/Livewire/CreateComment.php:

use App\Models\Post;
use Livewire\Component;
use Livewire\Attributes\Validate;
use Illuminate\Contracts\View\View;
 
class CreateComment extends Component
{
    public Post $post;
 
    #[Validate('required')]
    public string $body = '';
 
    public function save(): void
    {
        $this->validate();
 
        $this->post->comments()->create(['body' => $this->body]);
 
        $this->reset('body');
    }
 
    public function render(): View
    {
        return view('livewire.create-comment');
    }
}

Notice: As you can see in the CreateComment Livewire component, no mount() method exists. This is another alternative to reduce code. Livewire automatically sets $post to the correct Post from the Route Model Binding.

resources/views/livewire/create-comment.php:

<div class="mt-4">
    <form method="POST" wire:submit="save">
        <div>
            <label for="body" class="block font-medium text-sm text-gray-700">Body</label>
            <textarea id="body" wire:model="body" class="block mt-1 w-full border-gray-300 rounded-md shadow-sm"></textarea>
            @error('body')
                <span class="mt-2 text-sm text-red-600">{{ $message }}</span>
            @enderror
        </div>
 
        <button class="mt-4 px-4 py-2 bg-gray-800 rounded-md font-semibold text-xs text-white uppercase tracking-widest hover:bg-gray-700">
            Save
        </button>
    </form>
</div>

I will use it as a full-page Livewire component, so the Route would look like this.

routes/web.php:

Route::get('post/{post}', \App\Livewire\ViewPost::class);

After visiting the page, we have a similar result to the one below:

initial post view

Dispatching and Listening to the Events

After saving the comment, we need to trigger an event. This is done using the dispatch() method and passing the event's name.

app/Livewire/CreateComment.php:

class CreateComment extends Component
{
    // ...
 
    public function save(): void
    {
        $this->post->comments()->create(['body' => $this->body]);
 
        $this->dispatch('comment-added'); 
 
        $this->reset('body');
    }
 
    // ...
}

Notice: in the older Livewire v2, the method name was called ->emit(), in v3 it was changed to ->dispatch().

Now that event is triggered, we must listen for it in the ViewPost Livewire component. To do that, we need to add a #[On] attribute above the method that needs to be called.

app/Livewire/ViewPost.php:

use Livewire\Attributes\On;
 
class ViewPost extends Component
{
    // ...
 
    #[On('comment-added')]
    public function commentAdded(): void
    {
        $this->commentsCount++;
    }
 
    // ...
}

After saving the comment now, the comments count is incremented.

event is triggered

So, that's how you communicate between Livewire components: your page may consist of many individual smaller components, passing data between each other by dispatching events.

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Multiple Components: Dispatching Events

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Dispatching and Listening to the Events

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