Trait UserData

pub unsafe trait UserData<'js> {
    type Static: 'static + Any;

    // Provided methods
    unsafe fn to_static(this: Self) -> Self::Static
       where Self: Sized { ... }
    unsafe fn from_static_box(this: Box<Self::Static>) -> Box<Self>
       where Self: Sized { ... }
    unsafe fn from_static_ref<'a>(this: &'a Self::Static) -> &'a Self
       where Self: Sized { ... }
}

A trait for userdata which is stored in the runtime.

Safety

For safe implementation of this trait none of its default implemented functions must be overwritten and the type Static must be the correct type.

The static type must be the original type with the 'js lifetime changed to 'static.

All rquickjs javascript value have a 'js lifetime, this lifetime is managed by rquickjs to ensure that rquickjs values are used correctly. You can derive some lifetimes from this lifetimes but only lifetimes on rquickjs structs can be soundly changed by this trait.

If changing a values type to its UserData::Static type would cause any borrow, non-rquickjs struct with a ’js struct to no have a different lifetime then the implementation is unsound.

Example

Below is a correctly implemented UserData, the 'js on Function is directly derived from a Ctx<'js>.

struct MyUserData<'js>{
    function: Option<Function<'js>>
}

unsafe impl<'js> UserData<'js> for MyUserData<'js>{
    // The self type with the lifetime changed to static.
    type Static = MyUserData<'static>;
}

The example below is unsound as it changes the &'js borrow to static.

struct MyUserData<'js>{
    // This is unsound!
    // The &'js lifetime here is not a lifetime on a rquickjs struct.
    function: &'js Function<'js>
}

unsafe impl<'js> UserData<'js> for MyUserData<'js>{
    // The self type with the lifetime changed to static.
    type Static = MyUserData<'static>;
}

Required Associated Types

type Static: 'static + Any

Provided Methods

unsafe fn to_static(this: Self) -> Self::Static

where Self: Sized,

unsafe fn from_static_box(this: Box<Self::Static>) -> Box<Self>

where Self: Sized,

unsafe fn from_static_ref<'a>(this: &'a Self::Static) -> &'a Self

where Self: Sized,

Implementors