Struct Id 

pub struct Id<D: IdDomain> { /* private fields */ }

Lightweight, type-safe numeric identifier

Id<D> wraps a NonZeroU64 with a phantom domain marker, providing compile-time type safety for numeric identifiers. It is Copy, making it ideal for use as database primary keys, entity IDs, and similar use cases.

The non-zero invariant means Option<Id<D>> is the same size as Id<D> (niche optimization), and zero can never accidentally represent a valid ID.

Domain Trait

Id<D> uses IdDomain — a lightweight marker trait with only a domain name. No string validation or normalization needed, unlike KeyDomain.

Memory Layout

Id<D> struct (8 bytes, niche-optimized):
┌──────────────────┬─────────────┐
│ NonZeroU64 (8B)  │ marker (0B) │
└──────────────────┴─────────────┘

Option<Id<D>>: also 8 bytes (None = 0)

Type Safety

Different domains produce incompatible ID types at compile time:

use domain_key::{Id, Domain, IdDomain};

#[derive(Debug)]
struct UserDomain;
impl Domain for UserDomain { const DOMAIN_NAME: &'static str = "user"; }
impl IdDomain for UserDomain {}

#[derive(Debug)]
struct OrderDomain;
impl Domain for OrderDomain { const DOMAIN_NAME: &'static str = "order"; }
impl IdDomain for OrderDomain {}

type UserId = Id<UserDomain>;
type OrderId = Id<OrderDomain>;

let user_id = UserId::new(1).unwrap();
let order_id: OrderId = user_id; // Compile error!

Implementations

impl<D: IdDomain> Id<D>

pub const fn new(value: u64) -> Option<Self>

Creates a new typed identifier from a u64 value.

Returns None if value is zero.

Examples

use domain_key::{Id, Domain, IdDomain};

#[derive(Debug)]
struct UserDomain;
impl Domain for UserDomain { const DOMAIN_NAME: &'static str = "user"; }
impl IdDomain for UserDomain {}

type UserId = Id<UserDomain>;

assert!(UserId::new(1).is_some());
assert!(UserId::new(0).is_none());

pub const fn from_non_zero(value: NonZeroU64) -> Self

Creates a new typed identifier from a NonZeroU64 value.

pub const fn get(&self) -> u64

Returns the underlying value as u64.

pub const fn non_zero(&self) -> NonZeroU64

Returns the underlying NonZeroU64 value.

pub fn domain(&self) -> &'static str

Returns the domain name for this identifier type.

Trait Implementations

impl<D: IdDomain> Clone for Id<D>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<D: IdDomain> Debug for Id<D>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de, D: IdDomain> Deserialize<'de> for Id<D>

Available on crate feature serde only.

fn deserialize<De: Deserializer<'de>>( deserializer: De, ) -> Result<Self, De::Error>

Deserialize this value from the given Serde deserializer.

impl<D: IdDomain> Display for Id<D>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<D: IdDomain> From<Id<D>> for NonZeroU64

fn from(id: Id<D>) -> Self

Converts to this type from the input type.

impl<D: IdDomain> From<Id<D>> for u64

fn from(id: Id<D>) -> Self

Converts to this type from the input type.

impl<D: IdDomain> From<NonZero<u64>> for Id<D>

fn from(value: NonZeroU64) -> Self

Converts to this type from the input type.

impl<D: IdDomain> FromStr for Id<D>

type Err = IdParseError

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

impl<D: IdDomain> Hash for Id<D>

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<D: IdDomain> Ord for Id<D>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<D: IdDomain> PartialEq for Id<D>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<D: IdDomain> PartialOrd for Id<D>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<D: IdDomain> Serialize for Id<D>

Available on crate feature serde only.

fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.

impl<D: IdDomain> TryFrom<&str> for Id<D>

type Error = IdParseError

The type returned in the event of a conversion error.

fn try_from(s: &str) -> Result<Self, Self::Error>

Performs the conversion.

impl<D: IdDomain> TryFrom<String> for Id<D>

type Error = IdParseError

The type returned in the event of a conversion error.

fn try_from(s: String) -> Result<Self, Self::Error>

Performs the conversion.

impl<D: IdDomain> TryFrom<u64> for Id<D>

type Error = IdParseError

The type returned in the event of a conversion error.

fn try_from(value: u64) -> Result<Self, Self::Error>

Performs the conversion.

impl<D: IdDomain> Copy for Id<D>

impl<D: IdDomain> Eq for Id<D>