CODEWITHSUNDEEP
rust
Xcode23
Xcode23

Reputation: 381

How to implement a method that works for all struct type parameters?

I have the following struct

struct Position<T> {
    ns: i32,
    we: i32,
    orientation: T
}

I'd like to have the following method without having to repeat its implementation for each and every type T I intend to use, since the method implementation does not actually depend on T I would think this is possible to do but I can't figure out how.

impl Position {
    fn distance(&self) -> i32 {
        self.ns.abs() + self.we.abs()
    }
}

I have tried adding a type parameter to the impl line but apparently that only works for a concrete type not for a type variable which is what I would need here to do what I want I think. I have tried something along the lines of <_> but no dice either.

Is this possible to do in Rust?

Upvotes: 0

Views: 203

Answers (2)

Masklinn
Masklinn

Reputation: 42592

T is an intrinsic part of Position, so you need to impl Position<T>, but then T doesn't exist in the scope of the impl block (there is no intrinsic relationship between the struct and impl blocks, indeed they could use completely different parameter names), so you need to declare it:

impl<T> Position<T> {
    fn distance(&self) -> i32 {
        self.ns.abs() + self.we.abs()
    }
}

Upvotes: 2

user2722968
user2722968

Reputation: 16535

If you have methods on Position has apply to any T, you can place them in a impl that has no bounds:

impl<T> Position<T> {
    fn distance(&self) -> i32 {
        self.ns.abs() + self.we.abs()
    }
    
    // fn ....
}

Remember that you can have multiple impl blocks for a type. So if you have methods that require T to be bound, you can add

impl<T: Clone> Position<T> {
    // fn ...
}

Upvotes: 2

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