Generics

• Generics in Rust enable you to write flexible, reusable code that works with different data types while ensuring type safety.

• We use generics to create definitions for items like function signatures or structs, which we can then use with many different concrete data types.

• Represented by angle brackets (<>) and often denoted by T, U, or other descriptive names.

• Rust generates optimized code for each concrete type used with a generic at compile time, avoiding runtime overhead.

• References:

  • Generic Data Types

  • Bounds

generics1.rs

// `Vec<T>` is generic over the type `T`. In most cases, the compiler is able to
// infer `T`, for example after pushing a value with a concrete type to the vector.
// But in this exercise, the compiler needs some help through a type annotation.

fn main() {
    // Fix the compiler error by annotating the type of the vector
    // `Vec<T>`. Choose `T` as some integer type that can be created from
    // `u8` and `i8`.
    let mut numbers: Vec<i32> = Vec::new();

    // Don't change the lines below.
    let n1: u8 = 42;
    numbers.push(n1.into());
    let n2: i8 = -1;
    numbers.push(n2.into());

    println!("{numbers:?}");
}

• In this exercise we just need to define the vector type.

• We can use i32 that satisfy both u8 and i8 type that pushed in the main function.

generics2.rs

// This powerful wrapper provides the ability to store a positive integer value.
// Rewrite it using a generic so that it supports wrapping ANY type.
struct Wrapper<T> {
    value: T,
}

// Adapt the struct's implementation to be generic over the wrapped value.
impl<T> Wrapper<T> {
    fn new(value: T) -> Self {
        Wrapper { value }
    }
}

fn main() {
    // You can optionally experiment here.
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn store_u32_in_wrapper() {
        assert_eq!(Wrapper::new(42).value, 42);
    }

    #[test]
    fn store_str_in_wrapper() {
        assert_eq!(Wrapper::new("Foo").value, "Foo");
    }
}

• In this exercise we tasked to build Wrapper that accepts generics.

• So we need to add <T> in struct definition and the implementation to make it generics.