yew/docs/concepts/html/classes.md

title	description
Classes	A handy macro to handle classes

Classes

The struct Classes can be used to deal with HTML classes.

When pushing a string to the set, Classes ensures that there is one element for every class even if a single string might contain multiple classes.

Classes can also be merged by using Extend (i.e. classes1.extend(classes2)) or push() (i.e. classes1.push(classes2)). In fact, anything that implements Into<Classes> can be used to push new classes to the set.

The macro classes! is a convenient macro that creates one single Classes. Its input accepts a comma separated list of expressions. The only requirement is that every expression implements Into<Classes>.

html! {
  <div class=classes!("container")></div>
}

html! {
  <div class=classes!("class-1", "class-2")></div>
}

let my_classes = String::from("class-1 class-2");

html! {
  <div class=classes!(my_classes)></div>
}

html! {
  <div class=classes!(Some("class")) />
}

html! {
  <div class=classes!(vec!["class-1", "class-2"])></div>
}

let my_classes = ["class-1", "class-2"];

html! {
  <div class=classes!(&my_classes)></div>
}

Components that accept classes

use boolinator::Boolinator;

#[derive(Clone, Properties)]
struct Props {
    #[prop_or_default]
    class: Classes,
    fill: bool,
    children: Children,
}

struct MyComponent {
    props: Props,
}

impl Component for MyComponent {
    type Properties = Props;

    // ...

    fn view(&self) -> Html {
        let Props {
            class,
            fill,
            children,
        } = &self.props;
        html! {
            <div
                class=classes!(
                    "my-container-class",
                    fill.as_some("my-fill-class"),
                    class.clone(),
                )
            >
                { children.clone() }
            </div>
        }
    }
}

The example makes use of the boolinator crate to conditionally add the "my-fill-class" class based on the fill boolean attribute.