How do I access a struct field which has the same name as a public function?

Question

I'm trying to access the version of a particular clap::App I have instantiated. However, the field version exists as does the public function version()

Here is the relevant bits of source code:

pub struct App<'a, 'v, 'ab, 'u, 'h, 'ar> {
    // ...
    version: Option<&'v str>,
    // ...
}

impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
    // ...
    pub fn version(mut self, v: &'v str) -> Self {
        self.version = Some(v);
        self
    }
    // ...
}

And my code:

pub fn build_cli() -> App<'static, 'static> {
    App::new("my-pi")
        .version("0.1.0")
// ...

let app = build_cli();
assert_eq!(app.version, "0.1.0"); // <-- Error here

The field version and function version() both exist on App. How can this be? And how can I access the field version?

The error:

error[E0615]: attempted to take value of method `version` on type `clap::App<'_, '_>`
  --> src/cli.rs:27:21
   |
27 |         assert_eq!(app.version, "0.1.0");
   |                        ^^^^^^^
   |
   = help: maybe a `()` to call it is missing?

score 12 · Answer 1 · answered Oct 02 '18 at 19:41

You access a field that is named the same as a function by accessing the field:

struct Example {
    foo: i32,
}

impl Example {
    fn foo(&self) -> i32 {
        self.foo + 100
    }
}

fn main() {
    let ex = Example { foo: 42 };

    println!("{}", ex.foo);
    println!("{}", ex.foo());
}

It is assumed that, without the parenthesis, you want the field's value.

How do I access a struct field which has the same name as a public function?

2 Answers2