---
title: 'Children'
---

:::caution

Inspecting and manipulating `Children` can often result in surprising and hard-to-explain behaviours in your application.
This can lead to edge cases and often does not yield expected result.
You should consider other approaches if you are trying to manipulate `Children`.

Yew supports using `Html` as the type of the children prop.
You should use `Html` as children if you do not need `Children` or `ChildrenRenderer`.
It doesn't have the drawbacks of `Children` and has a lower performance overhead.

:::

## 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.

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

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

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">
                {ctx.props().children.clone()}
            </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>`.

```rust
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>
        }
    }
}
```

## Nested Children with Props

Nested component properties can be accessed and mutated if the containing component types its children.

```rust
use std::rc::Rc;
use yew::prelude::*;

#[derive(Clone, PartialEq, Properties)]
pub struct ListItemProps {
    value: String,
}

#[function_component]
fn ListItem(props: &ListItemProps) -> Html {
    let ListItemProps { value } = props.clone();
    html! {
        <span>
            {value}
        </span>
    }
}

#[derive(PartialEq, Properties)]
pub struct Props {
    pub children: ChildrenWithProps<ListItem>,
}

#[function_component]
fn List(props: &Props) -> Html {
    let modified_children = props.children.iter().map(|mut item| {
            let mut props = Rc::make_mut(&mut item.props);
            props.value = format!("item-{}", props.value);
            item
    });
    html! { for modified_children }
}

html! {
    <List>
        <ListItem value="a" />
        <ListItem value="b" />
        <ListItem value="c" />
    </List>
};
```

### 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`](https://github.com/JelteF/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.

```rust
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:

```rust
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 />
        }
    }
}
```

## Further Reading

- For a real-world example of this pattern, check out the yew-router source code. For a more advanced example, check out the [nested-list example](https://github.com/yewstack/yew/tree/master/examples/nested_list) in the main yew repository.
