Add a custom event to a component

7 minutes

Let's complete the application by adding a form. The form will have a drop-down list for the user to select their desired cabin, and a button to book the cruise. You'll set this up as a new component and create an event for the button. You'll finish by calling this new component from Host.vue.

Create the component

Start by creating the component.

In Visual Studio Code, create a file named BookingForm.vue in src/components.
In BookingForm.vue, type vue, and then select <vue> with default.vue from the snippets menu.

The snippet will create the default structure.

Add the code for the component

Let's add the code that the component will use, including registering the props, emits, data, and methods.

Open src/components/BookingForm.vue if it's not already open.
Inside the curly braces ({ }) for export default, add the following code to configure the component:
```
props: {
    cabins: Array,
},
emits: ['bookingCreated'],
data() {
    return {
        cabinIndex: -1
    }
},
methods: {
    bookCabin() {
        if(this.cabinIndex < 0) return;
        this.$emit('bookingCreated', this.cabinIndex);
        this.cabinIndex = -1;
    },
}
```
This code starts by creating a cabins prop to display the list of available cabins. We expose one event named bookingCreated by using emits. We create a data item named cabinIndex to store the selected cabin index.

We finish by creating a method named bookCabin. This method checks the value of cabinIndex and runs only if the value is 0 or greater (meaning that the user selected a cabin). If this validation passes, we emit the event returning the selected cabinIndex, and reset the cabinIndex to -1.

Add the display template

With the code added, we can turn our attention to the display. We want to have a drop-down list for cabin selection, and a button to book the trip. The button will call the bookCabin function that you created earlier.

Open src/components/BookingForm.vue if it's not already open.

Add the following code inside the <template> tags to create the display:

<section>
<h2>Book now!</h2>
<form>
    <div class="row">
        <label for="cruise-cabin">Select class:</label>
        <select id="cruise-cabin" v-model="cabinIndex">
            <option disabled value="-1">Select a cabin</option>
            <option v-for="(cabin, index) in cabins" :value="index" :key="index">
                {{ cabin.name }} $ {{ cabin.price.toLocaleString('en-US') }}
            </option>
        </select>
    </div>
    <div class="row">
        <button class="button" type="button" @click="bookCabin">Book now!</button>
    </div>
</form>
</section>

The HTML creates the form. We loop through the cabins prop by using v-for to create the drop-down list. We bind the model of the select tag to cabinIndex, which will be returned when the user selects a cabin and selects the button. We then set up the button to call bookCabin when it's selected.

Add BookingForm to the page

Finish by adding the newly created BookingForm to the application by adding it to Host.vue.

Open src/components/Host.vue.
Import BookingForm by adding the following code after the TODO: Register next component comment:
```
import BookingForm from './BookingForm.vue';
```
Add BookingForm to the list of available components by adding the following code after the TODO: Add next component comment:
```
BookingForm
```
Add the method to handle the bookingCreated custom event by adding the following code after the TODO: Add methods comment:
```
methods: {
    addBooking(cabinIndex) {
        const cabin = this.cruise.cabins[cabinIndex];
        const booking = {
            cabin: cabin.name,
            price: cabin.price
        }
        this.bookings.push(booking);
    }
}
```
The addBooking function retrieves the selected cabin by using the index. The function then creates a new booking object by using cabin.name and cabin.price. We then add booking to the bookings array.
Use the booking-form component by adding the following code after the TODO: Add booking-form comment:
```
<booking-form @booking-created="addBooking" :cabins="cruise.cabins"></booking-form>
```
We connect the addBooking function to the booking-created event, and we pass the list of cabins for display.

Display the cabin type

Let's modify the template to display the information for our bookings. Instead of the "Sample" booking message that we showed in the last exercise, we'll display the cabin type for each booking.

Open src/components/BookingList.vue.

Inside the <template> element, change the field name in the div from booking.name to booking.cabin:

<div class="row" v-for="(booking, index) in bookings" :key="index">
    <div>{{ booking.cabin }} </div>
</div>

Test the page

With all the code added, let's test the page!

Save all files by selecting File > Save all.
Go to http://localhost:8080 and refresh the page.
Select a cabin from the drop-down list and select the button.

Your new booking displays.

You've now created and called a component with a custom event!

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