json::from_value expected Value found &Value

[linuxaged]

When I try to deserialize an array to vector:

let data: Value = json::from_str(&s).unwrap();
let meshes = data.find("meshes").unwrap();
let mesh_array = meshes.as_array().unwrap();
let mesh = mesh_array[0].as_object().unwrap();

let vertices: Vec<f64> = (json::from_value (mesh.get("vertices").unwrap()) ).unwrap();

get the error:

src/main.rs:17:49: 17:78 error: mismatched types:
 expected `serde::json::value::Value`,
    found `&serde::json::value::Value`
(expected enum `serde::json::value::Value`,
    found &-ptr) [E0308]
src/main.rs:17     let vertices: Vec<f64> = (json::from_value (mesh.get("vertices").unwrap()) ).unwrap();
                                                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

unwrap().clone() works here, but it is very consuming right?
is there a pass-by-ref version json::from_value, how to deal with this?

[erickt]

There isn't a pass-by-ref because I want to retain the option to move strings out of the maps without copies. Do you need to deserialize into a Value? If not you could instead deserialize into a

#[derive(Deserialize)]
struct Mesh {...}

#[derive(Deserialize)]
struct Object {
   Meshes: Vec<Mesh>,
}

[linuxaged]

The reason I do deserializing by parsing fields one by one is serde not supporting defaults for missing struct fields or ignore unkown fields

if feature like these was added, deserializing will be much more comfortable and faster