Generic Types in Rust

Just like it’s name , generic types mean we can have a generic data type on something that we need. It could be in enum, function or other concept we’ve known so far.

Rust is strict type language, but on a certain case, we want to abstract our code to avoid duplication, maybe through a function. We can use this generic type to help on this case.

Syntax

In general , you’ll see as representation of generic data type. T itself just a variable name, it could be anything.

Example generic type in Struct

struct Point<T> {
    x: T,
    y: T,
}

fn main() {
    let integer = Point { x: 5, y: 10 };
    let float = Point { x: 1.0, y: 4.0 };
}

We make a Point struct with T generic type. In this case, x and y must have same data type, since they’re both T

If you want to have a different data type, we can use different variable as such

struct Point<T, U> {
    x: T,
    y: U,
}

Example generic type in Enum

For a single type

enum Option<T> {
    Some(T),
    None,
}

For multiple type

enum Result<T, E> {
    Ok(T),
    Err(E),
}

Example generic type in a method

struct Point<T> {
    x: T,
    y: T,
}

impl<T> Point<T> {
    fn x(&self) -> &T {
        &self.x
    }
}

fn main() {
    let p = Point { x: 5, y: 10 };

    println!("p.x = {}", p.x());
}