Describing the UI
Dioxus is a declarative framework. This means that instead of telling Dioxus what to do (e.g. to "create an element" or "set the color to red") we simply declare what we want the UI to look like using RSX.
You have already seen a simple example of RSX syntax in the "hello world" application:
// define a component that renders a div with the text "Hello, world!" fn App(cx: Scope) -> Element { cx.render(rsx! { div { "Hello, world!" } }) }
Here, we use the rsx!
macro to declare that we want a div element, containing the text "Hello, world!". Dioxus takes the RSX and constructs a UI from it.
RSX Features
RSX is very similar to HTML in that it describes elements with attributes and children. Here's an empty div
element in RSX, as well as the resulting HTML:
cx.render(rsx!(div { // attributes / listeners // children }))
Attributes
Attributes (and event handlers) modify the behavior or appearance of the element they are attached to. They are specified inside the {} brackets, using the name: value syntax. You can provide the value as a literal in the RSX:
cx.render(rsx!(img { src: "https://avatars.githubusercontent.com/u/79236386?s=200&v=4", class: "primary_button", width: "10px" }))
Note: All attributes defined in
dioxus-html
follow the snake_case naming convention. They transform theirsnake_case
names to HTML'scamelCase
attributes.
Note: Styles can be used directly outside of the
style:
attribute. In the above example,color: "red"
is turned intostyle="color: red"
.
Custom Attributes
Dioxus has a pre-configured set of attributes that you can use. RSX is validated at compile time to make sure you didn't specify an invalid attribute. If you want to override this behavior with a custom attribute name, specify the attribute in quotes:
cx.render(rsx!(div { "style": "width: 20px; height: 20px; background-color: red;", }))
Special Attributes
While most attributes are simply passed on to the HTML, some have special behaviors.
The HTML Escape Hatch
If you're working with pre-rendered assets, output from templates, or output from a JS library, then you might want to pass HTML directly instead of going through Dioxus. In these instances, reach for dangerous_inner_html
.
For example, shipping a markdown-to-Dioxus converter might significantly bloat your final application size. Instead, you'll want to pre-render your markdown to HTML and then include the HTML directly in your output. We use this approach for the Dioxus homepage:
// this should come from a trusted source let contents = "live <b>dangerously</b>"; cx.render(rsx! { div { dangerous_inner_html: "{contents}", } })
Note! This attribute is called "dangerous_inner_html" because it is dangerous to pass it data you don't trust. If you're not careful, you can easily expose cross-site scripting (XSS) attacks to your users.
If you're handling untrusted input, make sure to sanitize your HTML before passing it into
dangerous_inner_html
– or just pass it to a Text Element to escape any HTML tags.
Boolean Attributes
Most attributes, when rendered, will be rendered exactly as the input you provided. However, some attributes are considered "boolean" attributes and just their presence determines whether they affect the output. For these attributes, a provided value of "false"
will cause them to be removed from the target element.
So this RSX wouldn't actually render the hidden
attribute:
cx.render(rsx! { div { hidden: false, "hello" } })
Not all attributes work like this however. Only the following attributes have this behavior:
- allowfullscreen
- allowpaymentrequest
- async
- autofocus
- autoplay
- checked
- controls
- default
- defer
- disabled
- formnovalidate
- hidden
- ismap
- itemscope
- loop
- multiple
- muted
- nomodule
- novalidate
- open
- playsinline
- readonly
- required
- reversed
- selected
- truespeed
For any other attributes, a value of "false"
will be sent directly to the DOM.
Interpolation
Similarly to how you can format Rust strings, you can also interpolate in RSX text. Use {variable} to Display the value of a variable in a string, or {variable:?} to use the Debug representation:
let coordinates = (42, 0); let country = "es"; cx.render(rsx!(div { class: "country-{country}", left: "{coordinates.0:?}", top: "{coordinates.1:?}", // arbitrary expressions are allowed, // as long as they don't contain `{}` div { "{country.to_uppercase()}" }, div { "{7*6}" }, // {} can be escaped with {{}} div { "{{}}" }, }))
Children
To add children to an element, put them inside the {}
brackets after all attributes and listeners in the element. They can be other elements, text, or components. For example, you could have an ol (ordered list) element, containing 3 li (list item) elements, each of which contains some text:
cx.render(rsx!(ol { li {"First Item"} li {"Second Item"} li {"Third Item"} }))
- First Item
- Second Item
- Third Item
Fragments
You can render multiple elements at the top level of rsx!
and they will be automatically grouped.
cx.render(rsx!( p {"First Item"}, p {"Second Item"}, ))
First Item
Second Item
Expressions
You can include arbitrary Rust expressions as children within RSX that implements IntoDynNode. This is useful for displaying data from an iterator:
let text = "Dioxus"; cx.render(rsx!(span { text.to_uppercase(), // create a list of text from 0 to 9 (0..10).map(|i| rsx!{ i.to_string() }) }))
Loops
In addition to iterators you can also use for loops directly within RSX:
cx.render(rsx! { // use a for loop where the body itself is RSX div { // create a list of text from 0 to 9 for i in 0..3 { // NOTE: the body of the loop is RSX not a rust statement div { "{i}" } } } // iterator equivalent div { (0..3).map(|i| rsx!{ div { "{i}" } }) } })
If statements
You can also use if statements without an else branch within RSX:
cx.render(rsx! { // use if statements without an else if true { rsx!(div { "true" }) } })