Tuple Structs for Newtype Pattern

Snippet

Tuple Structs for Newtype Pattern

Tuple structs (also called newtype patterns) wrap a single value in a struct with named fields accessed by index (.0, .1, etc.). They provide type safety by creating distinct types that prevent mixing up parameters of the same underlying type, such as UserId versus Username both containing Strings.

snippet.rs

rust

struct UserId(u64);
struct Username(String);
struct Email(String);
 
fn main() {
    let id = UserId(42);
    let name = Username(String::from("alice"));
    let email = Email(String::from("[email protected]"));
    
    println!("User {} has email {}", name.0, email.0);
    
    let doubled = UserId(id.0 * 2);
    println!("Doubled ID: {}", doubled.0);
}

Breakdown

struct UserId(u64)

Newtype wrapper around u64 representing a user identifier

struct Username(String)

Newtype wrapper around String for username storage

struct Email(String)

Newtype wrapper around String for email address storage

let id = UserId(42)

Create a UserId instance containing the value 42

println!("User {} has email {}", name.0, email.0)

Access the inner String values using .0 index notation

let doubled = UserId(id.0 * 2)

Perform operations on the inner value and wrap result in new UserId

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Tuple Structs for Newtype Pattern

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