Why Your Bulma & Svelte Font Awesome Icons Aren't Re-Rendering: A Common Issue and How to Fix It
Are you using Bulma and Svelte to create a beautiful web application, but finding that your Font Awesome icons aren't updating when you expect them to? This is a common problem, and it often stems from a misunderstanding of how reactivity works in Svelte. Don't worry, with a little bit of understanding, you can easily fix this issue and have your icons dancing to your code's tune.
The Scenario: A Static Icon
Let's imagine you have a Svelte component that conditionally displays a Font Awesome icon based on a variable:
<script>
let showStar = false;
</script>
<button on:click={() => showStar = !showStar}>
{#if showStar}
<i class="fas fa-star"></i>
{/if}
</button>
You click the button, the showStar variable changes, but the icon remains stubbornly static. What's going on?
The Root Cause: Reactivity and Svelte's Magic
The issue lies in Svelte's reactive system. When you declare a variable with let, Svelte automatically tracks changes to its value. However, it doesn't track changes within the DOM itself. In our example, Svelte sees that the showStar variable is updated, but it doesn't see the change in the <i> element because it's directly within the template, not bound to a reactive variable.
The Solution: Reactive DOM Elements
To solve this, we need to tie the DOM element to a reactive variable. We can achieve this by using the # prefix to create a named element reference:
<script>
let showStar = false;
let icon; // Add a variable for the icon element
</script>
<button on:click={() => showStar = !showStar}>
{#if showStar}
<i class="fas fa-star" bind:this={icon}></i>
{/if}
</button>
{#if icon}
<div>
{showStar ? icon.classList.add('fas fa-star') : icon.classList.remove('fas fa-star')}
</div>
{/if}
In this modified code:
- We introduce a
iconvariable to store a reference to the<i>element usingbind:this. - We use a conditional block
{#if icon}to ensure that the icon element is only updated once it's available. - Within the conditional block, we add or remove the
fas fa-starclass from theiconelement based on theshowStarvariable.
Now, every time showStar changes, Svelte will update the icon element's class, effectively toggling the display of the Font Awesome icon.
Going Further: Reactive Class Manipulation
For more complex scenarios, consider using a reactive class manipulation library like classnames or clsx. These libraries can handle adding and removing multiple classes based on your conditions, making your code more readable and manageable.
Key Takeaways
- Svelte's reactivity works by tracking changes in variables, not the DOM itself.
- To make DOM elements reactive, use the
bind:thisdirective and manage their properties through reactive variables. - Libraries like
classnamescan enhance your reactive class management.
By understanding this subtle difference and applying the right techniques, you can easily ensure your Bulma and Svelte applications render Font Awesome icons smoothly and predictably. Happy coding!
