Events

Liveblade offers a robust event system that you can use to communicate between different components on the page. Because it uses browser events under the hood, you can also use Liveblade's event system to communicate even with plain vanilla JavaScript.

To trigger an event, you may use the emit() method from anywhere inside your component and listen for that event from any other component on the page.

Dispatching events

To dispatch an event from a Liveblade component, you can call the emit() method, passing it the event name and any additional data you want to send along with the event.

Below is an example of dispatching a post-created event from a PostCreate component:

from pyblade import liveblade

class PostCreate(liveblade.Component):

    def save(self):
        ...
        self.emit("post-created") 

In this example, when the emit() method is called, the post-created event will be emited, and every other component on the page that is listening for this event will be notified.

Pro tip

You may use the dispatch() method to dispatch events. It works the same way as emit(). Choose which makes sense to you !

You can pass additional data with the event by passing the data as the second parameter to the emit() method:

self.emit('post-created', title=post.title)

Listening for events

To listen for an event in a Liveblade component, add the @on decorator above the method you want to be called when a given event is dispatched:

from pyblade import liveblade

class Dashboard(liveblade.Component):

	@on('post-created') 
    def update_post_list(self, title: str):
        ...

Now, when the post-created event is dispatched from the PostCreate component, a network request will be triggered and the update_post_list() method will be called.

As you can see, additional data sent with the event will be provided to the method as its first argument.

Listening for dynamic event names

Occasionally, you may want to dynamically generate event listener names at run-time using data from your component.

For example, if you wanted to scope an event listener to a specific Database model, you could append the model's ID to the event name when dispatching like so:

from pyblade import liveblade
from app.models import Post


class PostUpdate(liveblade.Component):
    post: Post

    def update(self, id: int):
        ...
        self.emit(f"post-updated.{post.id}") 

And then listen for that specific model:

from pyblade import liveblade
from app.models import Post

class PostDetail(liveblade.Component):

    post: Post

	@on(f"post-updated.{post.id}") 
    def refresh_post(self):
        ...

If the above post model had an ID of 3, the refresh_post() method would only be triggered by an event named: post-updated.3.

Listening for events from specific child components

Liveblade allows you to listen for events directly on individual child components in your PyBlade template like so:

<div>
    <liveblade:edit-post b-saved="refresh">

    <!-- ... -->
</div>

In the above scenario, if the edit-post child component dispatches a saved event, the parent's refresh will be called and the parent will be refreshed.

Instead of passing refresh, you can pass any method you normally would to something like b-click. Here's an example of calling a close() method that might do something like close a modal dialog:

<liveblade:edit-post b-saved="close">

If the child dispatched parameters along with the request, for example self.emit('saved', post_id=1), you can forward those values to the parent method using the following syntax:

<liveblade:edit-post b-saved="close(event.detail.post_id)">

Dispatching directly to another component

If you want to use events for communicating directly between two components on the page, you can use the emit().to() modifier.

Below is an example of the PostCreate component dispatching the post-created event directly to the Dashboard component, skipping any other components listening for that specific event:

from pyblade import liveblade

class postCreate(liveblade.Component):

    def save(self):
		self.emit("post-created").to("Dashboard") 

Dispatching a component event to itself

Using the emit().self() modifier, you can restrict an event to only being intercepted by the component it was triggered from:

from pyblade import liveblade

class postCreate(liveblade.Component):

    def save(self):
		self.emit("post-created").self() 

Dispatching events from PyBlade templates

You can dispatch events directly from your PyBlade templates using the emit() function. This is useful when you want to trigger an event from a user interaction, such as a button click:

<button b-click="emit('show-post-modal', id={{ post.id }})">
    EditPost
</button>

In this example, when the button is clicked, the show-post-modal event will be dispatched with the specified data.

If you want to dispatch an event directly to another component you can use the emit().to() modifier:

<button b-click="emit('show-post-modal', id={{ post.id }}).to('PostList')">
    EditPost
</button>

In this example, when the button is clicked, the show-post-modal event will be dispatched directly to the PostList component.

Using JavaScript to interact with events

Liveblade's event system becomes much more powerful when you interact with it from JavaScript inside your application. This unlocks the ability for any other JavaScript in your app to communicate with Liveblade components on the page.

Listening for events inside component scripts

You can easily listen for the post-created event inside your component's template from a @script directive like so:

@script
<script>
    py.on('post-created', () => {
        //
    });
</script>
@endscript

The above snippet would listen for the post-created from the component it's registered within. If the component is no longer on the page, the event listener will no longer be triggered.

Dispatching events from component scripts

Additionally, you can dispatch events from within a component's @script like so:

@script
<script>
    py.emit('post-created');
</script>
@endscript

When the above @script is run, the post-created event will be dispatched to the component it's defined within.

To dispatch the event only to the component where the script resides and not other components on the page (preventing the event from "bubbling" up), you can use emit().self().

py.emit('post-created').self();

You can pass any additional parameters to the event by passing an object as a second argument to emit():

@script
<script>
    py.emit('post-created', { refresh_posts: true });
</script>
@endscript

You can now access those event parameters from both your Liveblade class and also other JavaScript event listeners.

Here's an example of receiving the refresh_posts parameter within a Liveblade class:

from pyblade import liveblade
# ...

    @on("post-created")
    def handle_new_post(self, refresh_posts: bool = false):
        ...

You can also access the refresh_posts parameter from a JavaScript event listener from the event's detail property:

@script
<script>
    py.on('post-created', (event) => {
        let refreshPosts = event.detail.refresh_posts

        // ...
    });
</script>
@endscript

Listening for Liveblade events from global JavaScript

Alternatively, you can listen for Liveblade events globally using Liveblade.on from any script in your application:

<script>
    document.addEventListener('liveblade:init', () => {
       Liveblade.on('post-created', (event) => {
           //
       });
    });
</script>

The above snippet would listen for the post-created event dispatched from any component on the page.

If you wish to remove this event listener for any reason, you can do so using the returned cleanup function:

<script>
    document.addEventListener('liveblade:init', () => {
        let cleanup = Liveblade.on('post-created', (event) => {
            //
        });

        // Calling "cleanup()" will un-register the above event listener...
        cleanup();
    });
</script>