HTML
The html!
macro allows you to write HTML and SVG code declaratively. It is similar to JSX
(an extension to JavaScript that allows you to write HTML-like code inside of JavaScript).
Important notes
- The
html!
macro only accepts one root html node (you can counteract this by using fragments or iterators) - An empty
html! {}
invocation is valid and will not render anything - Literals must always be quoted and wrapped in braces:
html! { <p>{ "Hello, World" }</p> }
- The
html!
macro will make all tag names lowercase. To use upper case characters (which are required for some SVG elements) use dynamic tag names:html! { <@{"myTag"}></@> }
The html!
macro can reach the default recursion limit of the compiler. If you encounter compilation errors,
add an attribute like #![recursion_limit="1024"]
in the crate root to overcome the problem.
Tag Structure
Tags are based on HTML tags. Components, Elements, and Lists are all based on this tag syntax.
Tags must either self-close <... />
or have a corresponding end tag for each start tag.
- Open - Close
- Invalid
use yew::prelude::*;
html! {
<div id="my_div"></div>
};
use yew::prelude::*;
html! {
<div id="my_div"> // <- MISSING CLOSE TAG
};
- Self-closing
- Invalid
use yew::prelude::*;
html! {
<input id="my_input" />
};
use yew::prelude::*;
html! {
<input id="my_input"> // <- MISSING SELF-CLOSE
};
For convenience, elements which usually require a closing tag are allowed to self-close. For example, writing html! { <div class="placeholder" /> }
is valid.
Children
Create complex nested HTML and SVG layouts with ease:
- HTML
- SVG
use yew::prelude::*;
html! {
<div>
<div data-key="abc"></div>
<div class="parent">
<span class="child" value="anything"></span>
<label for="first-name">{ "First Name" }</label>
<input type="text" id="first-name" value="placeholder" />
<input type="checkbox" checked=true />
<textarea value="write a story" />
<select name="status">
<option selected=true disabled=false value="">{ "Selected" }</option>
<option selected=false disabled=true value="">{ "Unselected" }</option>
</select>
</div>
</div>
};
use yew::prelude::*;
html! {
<svg width="149" height="147" viewBox="0 0 149 147" fill="none" xmlns="http://www.w3.org/2000/svg">
<path d="M60.5776 13.8268L51.8673 42.6431L77.7475 37.331L60.5776 13.8268Z" fill="#DEB819"/>
<path d="M108.361 94.9937L138.708 90.686L115.342 69.8642" stroke="black" stroke-width="4" stroke-linecap="round" stroke-linejoin="round"/>
<g filter="url(#filter0_d)">
<circle cx="75.3326" cy="73.4918" r="55" fill="#FDD630"/>
<circle cx="75.3326" cy="73.4918" r="52.5" stroke="black" stroke-width="5"/>
</g>
<circle cx="71" cy="99" r="5" fill="white" fill-opacity="0.75" stroke="black" stroke-width="3"/>
<defs>
<filter id="filter0_d" x="16.3326" y="18.4918" width="118" height="118" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
<@{"feGaussianBlur"} stdDeviation="2"/>
<@{"feColorMatrix"} in="SourceAlpha" type="matrix" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0"/>
</filter>
</defs>
</svg>
};
Lints
If you compile Yew using a nightly version of the Rust compiler, the macro will warn you about some
common pitfalls that you might run into. Of course, you may need to use the stable compiler (e.g.
your organization might have a policy mandating it) for release builds, but even if you're using a
stable toolchain, running cargo +nightly check
might flag some ways that you could improve your
HTML code.
At the moment the lints are mostly accessibility-related. If you have ideas for lints, please feel free to chime in on this issue.
Specifying attributes and properties
Attributes are set on elements in the same way as in normal HTML:
use yew::prelude::*;
let value = "something";
html! { <div attribute={value} /> };
Properties are specified with ~
before the element name:
use yew::prelude::*;
html! { <my-element ~property="abc" /> };
The braces around the value can be ommited if the value is a literal.
Literals are all valid literal expressions
in Rust. Note that negative numbers are not literals
and thus must be encosed in curly-braces {-6}
Component properites are passed as Rust objects and are different from the element attributes/properties described here. Read more about them at Component Properties
Special properties
There are special properties which don't directly influence the DOM but instead act as instructions to Yew's virtual DOM.
Currently, there are two such special props: ref
and key
.
ref
allows you to access and manipulate the underlying DOM node directly. See Refs for more details.
key
on the other hand gives an element a unique identifier which Yew can use for optimization purposes.
Read more at Lists
Conditional Rendering
Markup can be rendered conditonally by using Rust's conditional structures. ' +
'Currently only if
and if let
are supported.
use yew::prelude::*;
html! {
if true {
<p>{ "True case" }</p>
}
};
Read more at Conditonal Rendering