Unable to get past borrow issue

1

I have a root struct that references another struct through a HashMap which has a vector of service struct. I can't get the code to update the vector and fails with a borrow problem. This seems to be a typical way to keep data so I am having trouble seeing why updating the vector is such an issue.

use std::collections::HashMap;

#[derive(Debug, Clone)]
struct Service {
    url: String,
    token: String,
}

#[derive(Debug, Clone)]
struct Protobuf {
    name: String,
    instances: Vec<Service>,
}

impl Protobuf {
    fn add_service(&mut self, service: Service) {
        self.instances.push(service);
    }
}

#[derive(Debug, Clone)]
pub struct RootNode {
    protobuf_map: HashMap<String, Protobuf>,
}
impl RootNode {
    fn new() -> RootNode {
        RootNode {
            protobuf_map: HashMap::new(),
        }
    }
    fn add_protobuf(&mut self, key: &str, protobuf: Protobuf) {
        self.protobuf_map.insert(key.to_string(), protobuf);
    }
}

fn main() {
    let mut root = RootNode::new();

    let protobuf1 = Protobuf {
        name: "proto1".to_string(),
        instances: vec!(),
    };

    root.add_protobuf("proto1", protobuf1);

    // How to get this service struct added to proto1 vec array
    let serv = Service{
        url: "localhost:8080".to_string(),
        token: "token".to_string(),
    };

    let proto= root.protobuf_map.get("proto1").unwrap();
    println!("{:?}", proto);

   // fails at this point. 
    proto.add_service(serv);
}
2

You need to get a &mut _ reference to the Protobuf.

-    let proto = root.protobuf_map.get("proto1").unwrap();
+    let proto = root.protobuf_map.get_mut("proto1").unwrap();

P.s. please read the pinned code formatting guide.

3

Thank you for the reply. It works now!!