给出生命周期的编译器在结构中询问生命周期

Question

I'm trying to write the examples in the book "SFML Game Development" but I'm having a problem with the lifetimes for the struct that's supposed to represent the game world. The error is as follows:

extern crate sfml;

use self::sfml::window::*;
use self::sfml::graphics::*;

pub struct Game<'s> {
    mWindow: RenderWindow,
    mPlayer: &'s CircleShape,
}

Error message:

error[E0106]: missing lifetime specifier
 --> src/game.rs:8:18
  |
8 |     mPlayer: &'s CircleShape,
  |                  ^^^^^^^^^^^ expected lifetime parameter

Why is it asking for a lifetime if I have given it one?

Answer 1

Why is it asking for a lifetime if I have given it one?

Because you haven't given it the lifetime where it's needed. Look closely at the error message. It's telling you that CircleShape is missing a lifetime, not the reference to CircleShape (although that's also needed).

Review the definition of CircleShape :

pub struct CircleShape<'s> { /* fields omitted */ }

It has been parameterized by a lifetime, so you need to provide one:

pub struct Game<'s> {
    mWindow: RenderWindow,
    mPlayer: &'s CircleShape<'s>,
}

Whether that's correct for your case, I can't say, but it should compile.