Wrapping session creation in a factory

[MainRo]

Hello there,

Thanks for bringing this rust wrapper! I would like to expose a model object that is built from a helper. Up to now, I did not manage to implement such a simple code. I am almost sure that this is due to a lack of rust knowledge, and especially lifetimes. Here is my code:

use onnxruntime::{LoggingLevel, GraphOptimizationLevel};
use onnxruntime::environment::Environment;
use onnxruntime::session::Session;

pub struct Model<'a> {
    environment: Environment,
    session: Session<'a>,
}


impl<'a> Model<'a> {
    pub fn new() -> Model<'a> {
        let environment = Environment::builder()
            .with_name("foo")
            .with_log_level(LoggingLevel::Verbose)
            .build().expect("building environment");

        let session = environment.new_session_builder().unwrap()
            .with_optimization_level(GraphOptimizationLevel::Basic).unwrap()
            .with_number_threads(1).unwrap()
            .with_model_from_file("foo.onnx").unwrap();

        Model {
            environment: environment,
            session: session,
        }
    }

    //pub fn set_model(self, model_path: &String)
    //pub fn run(self, tensors)
}

This is in a dedicated module. When I try to use it from another function, I have this compilation error:

error[E0515]: cannot return value referencing local variable `environment`
  --> src/model.rs:23:9
   |
18 |           let session = environment.new_session_builder().unwrap()
   |                         ----------- `environment` is borrowed here
...
23 | /         Model {
24 | |             environment: environment,
25 | |             session: session,
26 | |         }
   | |_________^ returns a value referencing data owned by the current function

All the examples I found allocate the environment and the session objects as local variables in main. Moreover, the environment is used only once. I would like to build them indirectly and update the session (So I need to re-use the environment).
Can anybody give me some hints on how I can allocate a Model object that contains the environment and session objects in it? I tried to Box the environment object, and to put the session in an Option to defer its creation without success.

Thanks.