Lightningjs

Appearance

Directives ​

Blits comes with a few built-in attributes that tap into specific behaviour provided by the framework - also known as directives. Most of them can be used in the template on both Elements and Components.

Show-directive ​

The show attribute allows you to conditionally show and hide Components and Elements.

When passed a truthy value, such as true or 1, the element will be made visible. And when passed a falsey value (false or 0) it will not be visible.

xml
<Element>
  <Element w="100" h="100" color="purple" :show="$active"></Element>
  <Element w="100" h="100" y="200" color="purple" show="false"></Element>
</Element>

Is-directive ​

The is directive allows you to dynamically instantiate a Component based on a state variable or a passed prop.

It is very useful in combination with API driven Apps, where the type of Component to use, depends on what data is returned (i.e. a Poster or a HeroImage).

The is-component should always be used together with the built-in Component-tag.

js
export default Blits.Component('DynamicComponents', {
  template: `
    <Element>
      <Component is="$firstComponent" />
      <Component is="$secondComponent" x="500" />
    </Element>
  `,
  props: ['firstComponent', 'secondComponent'],
})

At the moment it's not possible to use the is-attribute as a reactive attribute and have a component change type after instantiation.

Ref-attribute ​

The declarative coding style that is promoted in Blits components, should generally remove the need to directly interact with individual Elements or Components in your template. However, in some cases you may need to reference them directly. For example, in order to delegate the focus.

For this use case, you can specify a ref-attribute on Elements (or Components). And by using the helper function this.select(), which is vailable on every Blits component, you can gain access to the child Element or Component inside your business logic.

The select()-function accepts the ref-value that you are looking for as a single argument, and returns the Element or Component if found.