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Version: Next

Children

General usage

Most of the time, when allowing a component to have children, you don't care what type of children the component has. In such cases, the below example will suffice.

use yew::{html, Children, Component, Context, Html, Properties};

#[derive(Properties, PartialEq)]
pub struct ListProps {
#[prop_or_default]
pub children: Children,
}

pub struct List;

impl Component for List {
type Message = ();
type Properties = ListProps;

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, ctx: &Context<Self>) -> Html {
html! {
<div class="list">
{ for ctx.props().children.iter() }
</div>
}
}
}

Advanced usage

Typed children

In cases where you want one type of component to be passed as children to your component, you can use yew::html::ChildrenWithProps<T>.

use yew::{html, ChildrenWithProps, Component, Context, Html, Properties};

pub struct Item;

impl Component for Item {
type Message = ();
type Properties = ();

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, _ctx: &Context<Self>) -> Html {
html! {
{ "item" }
}
}
}

#[derive(Properties, PartialEq)]
pub struct ListProps {
#[prop_or_default]
pub children: ChildrenWithProps<Item>,
}

pub struct List;

impl Component for List {
type Message = ();
type Properties = ListProps;

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, ctx: &Context<Self>) -> Html {
html! {
<div class="list">
{ for ctx.props().children.iter() }
</div>
}
}
}

Enum typed children

Of course, sometimes you might need to restrict the children to a few different components. In these cases, you have to get a little more hands-on with Yew.

The derive_more crate is used here for better ergonomics. If you don't want to use it, you can manually implement From for each variant.

use yew::{
html, html::ChildrenRenderer, virtual_dom::VChild, Component,
Context, Html, Properties,
};

pub struct Primary;

impl Component for Primary {
type Message = ();
type Properties = ();

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, _ctx: &Context<Self>) -> Html {
html! {
{ "Primary" }
}
}
}

pub struct Secondary;

impl Component for Secondary {
type Message = ();
type Properties = ();

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, _ctx: &Context<Self>) -> Html {
html! {
{ "Secondary" }
}
}
}

#[derive(Clone, derive_more::From, PartialEq)]
pub enum Item {
Primary(VChild<Primary>),
Secondary(VChild<Secondary>),
}

// Now, we implement `Into<Html>` so that yew knows how to render `Item`.
#[allow(clippy::from_over_into)]
impl Into<Html> for Item {
fn into(self) -> Html {
match self {
Self::Primary(child) => child.into(),
Self::Secondary(child) => child.into(),
}
}
}

#[derive(Properties, PartialEq)]
pub struct ListProps {
#[prop_or_default]
pub children: ChildrenRenderer<Item>,
}

pub struct List;

impl Component for List {
type Message = ();
type Properties = ListProps;

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, ctx: &Context<Self>) -> Html {
html! {
<div class="list">
{ for ctx.props().children.iter() }
</div>
}
}
}

Optional typed child

You can also have a single optional child component of a specific type too:

use yew::{
html, html_nested, virtual_dom::VChild, Component,
Context, Html, Properties
};

pub struct PageSideBar;

impl Component for PageSideBar {
type Message = ();
type Properties = ();

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, _ctx: &Context<Self>) -> Html {
html! {
{ "sidebar" }
}
}
}

#[derive(Properties, PartialEq)]
pub struct PageProps {
#[prop_or_default]
pub sidebar: Option<VChild<PageSideBar>>,
}

struct Page;

impl Component for Page {
type Message = ();
type Properties = PageProps;

fn create(_ctx: &Context<Self>) -> Self {
Self
}

fn view(&self, ctx: &Context<Self>) -> Html {
html! {
<div class="page">
{ ctx.props().sidebar.clone().map(Html::from).unwrap_or_default() }
// ... page content
</div>
}
}
}

// The page component can be called either with the sidebar or without:

pub fn render_page(with_sidebar: bool) -> Html {
if with_sidebar {
// Page with sidebar
html! {
<Page sidebar={html_nested! {
<PageSideBar />
}} />
}
} else {
// Page without sidebar
html! {
<Page />
}
}
}