JS style static property for Rust struct

Question

In javascript we can use the static keyword to define a static method or property for a class. Neither static methods nor static properties can be called on instances of the class. Instead, they're called on the class itself. So, for instance, we could count the number of instances of a certain class we've created:

class Player{
    static playerCount = 0;

    constructor(){
        Player.playerCount ++;
    }

}

Is their anything in rust that would roughly equivalent to this? Or possibly a library/macro that allows for something similar?

struct Player{}
impl Player{
    static playerCount;
    pub fn new()->Self{
        playerCount ++
        //increment playerCount 
    }
}

Rust does not support static fields in structures

chenzhongpu
– chenzhongpu

2021-06-09 02:07:48 +00:00
Commented Jun 9, 2021 at 2:07 — chenzhongpu
– chenzhongpu, Commented Jun 9, 2021 at 2:07

c-x-berger · Accepted Answer · 2021-06-09 04:42:41Z

1

There isn't such a thing as a static field in a Rust struct. Rust's structs are closer to their C namesake than the classes you'd find in object-oriented languages.

The rough equivalent is probably a static mut variable, which requires the use of unsafe code. This is because a globally accessible, mutable value is going to be a source of undefined behavior (such as data races) and Rust wants all code to be free of UB unless you write the word unsafe.

For your use case, perhaps a PlayerManager struct which holds this state and is passed by &mut reference to the new function is a good idea.

struct PlayerManager {
    count: usize,
}

impl PlayerManager {
    pub fn add_player(&mut self) {
        self.count += 1;
    }
}

// then...
impl Player {
    pub fn new(manager: &mut PlayerManager) -> Self {
        manager.add_player();
        // TODO: the rest of player construction
    }
}

edited Jun 9, 2021 at 4:42

answered Jun 9, 2021 at 2:24

c-x-berger

1,09114 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

ANimator120 Over a year ago

Yes, I was thinking that some kind of Manager struct would be my next recourse. Any chance you could add some example code that illustrates your description of PlayerManger?

c-x-berger Over a year ago

@ANimator120 I've added an example, but it's fairly simplistic (and was initially left out since I didn't think it was needed for this answer).

Collectives™ on Stack Overflow

JS style static property for Rust struct

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related