Struct Expr 

pub struct Expr<T> { /* private fields */ }

A value with a JavaScript expression that can produce it in the browser.

Expressions that read no signals render as static content. Their JavaScript remains available when needed for browser execution.

Implementations

impl<T> Expr<T>

pub fn evaluate(evaluate: impl FnOnce() -> T, js: Js) -> Self

Evaluates an expression while observing signal reads.

The evaluation is synchronous. Its signal reads must represent the dependencies of the JavaScript expression as well.

pub fn is_static(&self) -> bool

Whether this expression is known not to require reactive evaluation.

Signal reads during evaluate make it dynamic.

pub fn dynamic(self) -> Self

Makes this expression dynamic even if it reads no signals.

A static expression only renders its value. A dynamic one is also evaluated in the browser whenever its content renders. As a bind attribute, this sets the element’s live state on every render, such as the value of an input the user has edited, instead of only its default.

use topcoat::{Result, context::Cx, runtime::Expr, view::*};

#[component]
async fn search(cx: &Cx) -> Result<impl View> {
    // Every render clears what the user typed.
    let query = Expr::from(String::new()).dynamic();

    Ok(view! { <input :value=(query)> })
}

pub fn into_evaluated_and_js(self) -> (T, Js)

Returns the value and its JavaScript, including for static expressions.

Trait Implementations

impl<T: Clone> Clone for Expr<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Expr<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> From<T> for Expr<T>

where T: Surrogated, T::Surrogate: Serialize,

fn from(value: T) -> Self

Creates a static expression from a value in the runtime vocabulary.

Panics

Panics if the value’s surrogate cannot be serialized.

impl<T> NodeViewParts for Expr<T>

where T: NodeViewParts,

fn into_view_parts(self, cx: &Cx, parts: &mut PartsWriter<'_>)

Appends this value to the view being built.