Builder pattern

[erwanvivien]

How could you do a builder pattern using Wasm-Bindgen ?

I tried the basic:

#[wasm_bindgen]
pub struct Options {
    pub margin: u32,

    #[wasm_bindgen(getter_with_clone)]
    pub background_color: String,
}

#[wasm_bindgen]
impl Options {
    #[wasm_bindgen(constructor)]
    pub fn new() -> Options {
        Options {
            margin: 4,
            background_color: String::new(),
        }
    }

    pub fn set_margin(&mut self, margin: u32) -> *mut Options {
        self.margin = margin;
        self
    }
    
    
    pub fn set_background_color(&mut self, background_color: String) -> *mut Options {
        self.background_color = background_color;
        self
    }
}

It doesn't seem to work, in JS: I tried to print the values:

const tmp = new Options();
console.log(tmp);
console.log(tmp.set_margin(8))

FIRST PRINT: (wasm:32:17)
{
  "ptr": 1193996
}

SECOND PRINT: (wasm:33:17)
1194000