[−][src]Trait wasm_bindgen::JsCast

pub trait JsCast where
    Self: AsRef<JsValue> + Into<JsValue>, {
    fn instanceof(val: &JsValue) -> bool;

    fn unchecked_from_js(val: JsValue) -> Self;

    fn unchecked_from_js_ref(val: &JsValue) -> &Self;

    fn is_instance_of<T>(&self) -> bool
    where
        T: JsCast,
    { ... }

    fn dyn_into<T>(self) -> Result<T, Self>
    where
        T: JsCast,
    { ... }

    fn dyn_ref<T>(&self) -> Option<&T>
    where
        T: JsCast,
    { ... }

    fn unchecked_into<T>(self) -> T
    where
        T: JsCast,
    { ... }

    fn unchecked_ref<T>(&self) -> &T
    where
        T: JsCast,
    { ... }
}

A trait for checked and unchecked casting between JS types.

Specified in an RFC this trait is intended to provide support for casting JS values between differnet types of one another. In JS there aren't many static types but we've ascribed JS values with static types in Rust, yet they often need to be switched to other types temporarily! This trait provides both checked and unchecked casting into various kinds of values.

This trait is automatically implemented for any type imported in a #[wasm_bindgen] extern block.

Required methods

fn instanceof(val: &JsValue) -> bool

Performs a dynamic instanceof check to see whether the JsValue provided is an instance of this type.

This is intended to be an internal implementation detail, you likely won't need to call this.

fn unchecked_from_js(val: JsValue) -> Self

Performs a zero-cost unchecked conversion from a JsValue into an instance of Self

This is intended to be an internal implementation detail, you likely won't need to call this.

fn unchecked_from_js_ref(val: &JsValue) -> &Self

Performs a zero-cost unchecked conversion from a &JsValue into an instance of &Self.

Note the safety of this method, which basically means that Self must be a newtype wrapper around JsValue.

This is intended to be an internal implementation detail, you likely won't need to call this.

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Provided methods

fn is_instance_of<T>(&self) -> bool where
    T: JsCast, 

Test whether this JS value is an instance of the type T.

This method performs a dynamic check (at runtime) using the JS instanceof operator. This method returns self instanceof T.

fn dyn_into<T>(self) -> Result<T, Self> where
    T: JsCast, 

Performs a dynamic cast (checked at runtime) of this value into the target type T.

This method will return Err(self) if self.is_instance_of::<T>() returns false, and otherwise it will return Ok(T) manufactured with an unchecked cast (verified correct via the instanceof operation).

fn dyn_ref<T>(&self) -> Option<&T> where
    T: JsCast, 

Performs a dynamic cast (checked at runtime) of this value into the target type T.

This method will return None if self.is_instance_of::<T>() returns false, and otherwise it will return Some(&T) manufactured with an unchecked cast (verified correct via the instanceof operation).

fn unchecked_into<T>(self) -> T where
    T: JsCast, 

Performs a zero-cost unchecked cast into the specified type.

This method will convert the self value to the type T, where both self and T are simple wrappers around JsValue. This method does not check whether self is an instance of T. If used incorrectly then this method may cause runtime exceptions in both Rust and JS, this should be used with caution.

fn unchecked_ref<T>(&self) -> &T where
    T: JsCast, 

Performs a zero-cost unchecked cast into a reference to the specified type.

This method will convert the self value to the type T, where both self and T are simple wrappers around JsValue. This method does not check whether self is an instance of T. If used incorrectly then this method may cause runtime exceptions in both Rust and JS, this should be used with caution.

This method, unlike unchecked_into, does not consume ownership of self and instead works over a shared reference.

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Implementors

impl JsCast for JsValue[src]

fn is_instance_of<T>(&self) -> bool where
    T: JsCast, [src]

fn dyn_into<T>(self) -> Result<T, Self> where
    T: JsCast, [src]

fn dyn_ref<T>(&self) -> Option<&T> where
    T: JsCast, [src]

fn unchecked_into<T>(self) -> T where
    T: JsCast, [src]

fn unchecked_ref<T>(&self) -> &T where
    T: JsCast, [src]

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