getter and setter

The getter and setter attributes can be used in Rust impl blocks to define properties in JS that act like getters and setters of a field. For example:

#![allow(unused)]
fn main() {
#[wasm_bindgen]
pub struct Baz {
    field: i32,
}

#[wasm_bindgen]
impl Baz {
    #[wasm_bindgen(constructor)]
    pub fn new(field: i32) -> Baz {
        Baz { field }
    }

    #[wasm_bindgen(getter)]
    pub fn field(&self) -> i32 {
        self.field
    }

    #[wasm_bindgen(setter)]
    pub fn set_field(&mut self, field: i32) {
        self.field = field;
    }
}
}

Can be combined in JavaScript like in this snippet:

const obj = new Baz(3);
assert.equal(obj.field, 3);
obj.field = 4;
assert.equal(obj.field, 4);

You can also configure the name of the property that is exported in JS like so:

#![allow(unused)]
fn main() {
#[wasm_bindgen]
impl Baz {
    #[wasm_bindgen(getter = anotherName)]
    pub fn field(&self) -> i32 {
        self.field
    }

    #[wasm_bindgen(setter = anotherName)]
    pub fn set_field(&mut self, field: i32) {
        self.field = field;
    }
}
}

Getters are expected to take no arguments other than &self and return the field’s type. Setters are expected to take one argument other than &mut self (or &self) and return no values.

The name for a getter is by default inferred from the function name it’s attached to. The default name for a setter is the function’s name minus the set_ prefix, and if set_ isn’t a prefix of the function it’s an error to not provide the name explicitly.