How to use struct self in member method closure

Question

How can I call a method in closure? get_access_token method can set new access token based on self.get_base_url():

fn fetch_access_         


        

Answer 1

I'd use something like this instead:

Playground

fn fetch_access_token(base_url: &str) -> Result {
    let _url = format!("{}/v3/auth/token", base_url);
    // ...
    let token = String::from("test token");
    Ok(token)
}

fn get_env_url() -> String {
    String::from("http://www.test.com")
}

pub struct App {
    // private fields!
    base_url: String,
    access_token: Option,
}

impl App {
    pub fn new() -> App {
        App {
            base_url: get_env_url(),
            access_token: None,
        }
    }

    /// set new base url; clears cached access token
    pub fn set_base_url(&mut self, base_url: String) {
        self.base_url = base_url;
        self.access_token = None;
    }

    pub fn get_base_url(&self) -> &str {
        &self.base_url
    }

    /// retrieve (possibly cached) access token. tries again if previous attempt failed.
    pub fn retrieve_access_token(&mut self) -> Result<&str, ()> {
        if self.access_token.is_none() {
            self.access_token = Some(fetch_access_token(&self.base_url)?);
        }
        Ok(self.access_token.as_ref().unwrap())
    }
}

fn main() {
    let mut app = App::new();
    println!("{}", app.retrieve_access_token().unwrap());
}