entid

A Rust library for generating and validating type-safe, prefixed entity identifiers based on UUIDs and ULIDs.

Features

• Type-safe entity IDs: Create distinct ID types for different entities
• Multiple identifier formats: Support for both UUID and ULID
• Prefix support: Automatically add entity-specific prefixes to IDs
• Performance optimized: Thread-safe caching of string representations
• Serde compatible: Seamless serialization and deserialization
• Comprehensive error handling: Clear error types for all operations
• Zero-cost abstractions: Minimal runtime overhead
• Derive macro for implementing the Prefix trait: Optional

Installation

Add this to your Cargo.toml:

[dependencies]
entid = "0.4.2"

To use the derive macro for implementing the Prefix trait, enable the derive feature:

[dependencies]
entid = { version = "0.4.2", features = ["derive"] }

API Overview

The EntityId type provides several methods for working with entity IDs:

type UserId = UuidEntityId::<User>;

// Create a new EntityId
let user_id = UserId::generate();

// Get the full ID string with prefix (e.g., "user_123e4567-e89b-12d3-a456-426614174000")
let full_id = user_id.as_str();

// Get just the identifier part without the prefix (e.g., "123e4567-e89b-12d3-a456-426614174000")
let raw_id = user_id.id_str();

// Get a reference to the underlying identifier object
let identifier = user_id.identifier();

// Get the identifier string directly from the identifier
let id_str = user_id.identifier().as_str();

// Get the prefix for this entity type
let prefix = UserId::prefix(); // "user"

// Get the delimiter for this entity type
let delimiter = UserId::delimiter(); // "_"

// For ULID-based IDs, get the timestamp
if let Some(timestamp_ms) = ulid_id.timestamp_ms() {
    println!("ID created at: {} ms since epoch", timestamp_ms);
}

Flexible Creation Methods

The library provides multiple ways to create entity IDs:

use entid::{EntityId, Identifier, Prefix, UuidEntityId, UlidEntityId, Uuid, Ulid};

type UserId = UuidEntityId::<User>;

// Using the generate method
let user_id1 = UserId::generate();

// Using the new method with flexible string types (with prefix)
let id_str = "user_123e4567-e89b-12d3-a456-426614174000";
let user_id2 = UserId::new(id_str).unwrap();
let user_id3 = UserId::new(id_str.to_string()).unwrap();

// Using from_raw_str to parse a raw identifier string (without prefix)
let raw_uuid = "123e4567-e89b-12d3-a456-426614174000";
let user_id4 = UserId::from_raw_str(raw_uuid).unwrap();

// Using parse_raw_str with custom error handling
let user_id5 = UserId::parse_raw_str(raw_uuid, |e| format!("Invalid UUID: {}", e)).unwrap();

// Using TryFrom trait
let user_id6 = UserId::try_from(id_str).unwrap();
let user_id7 = UserId::try_from(id_str.to_string()).unwrap();

// Using FromStr trait
let user_id8 = id_str.parse::<UuidEntityId<User>>().unwrap();

// Using convenience methods
let uuid = Uuid::new_v4();
let user_id9 = UserId::with_uuid(uuid);
let user_id10 = UserId::new_v4();
let user_id11 = UserId::new_v5(&Uuid::NAMESPACE_DNS, "example.com");

// Using the builder pattern
let user_id12 = UserId::builder().build();
let user_id13 = UserId::builder().with_uuid(uuid).build();
let user_id14 = UserId::builder().with_uuid_v4().build();
let user_id15 = UserId::builder().with_uuid_v5(&Uuid::NAMESPACE_DNS, "example.com").build();

// For ULID-based IDs
type PostId = UlidEntityId::<Post>;

let ulid = Ulid::new();
let post_id1 = PostId::with_ulid(ulid);
let post_id2 = PostId::with_timestamp(1625097600000); // July 1, 2021
let post_id3 = PostId::monotonic_from(Some(&post_id2));

// Using the builder pattern for ULID
let post_id4 = PostId::builder().with_ulid(ulid).build();
let post_id5 = PostId::builder().with_timestamp(1625097600000).build();
let post_id6 = PostId::builder().with_monotonic_from(Some(&post_id5)).build();

Using EntityId in Collections

The EntityId type implements Borrow<str> and AsRef<str>, making it easy to use in collections:

use std::collections::{HashMap, HashSet};

// Use EntityId as a key in a HashMap
let mut user_map = HashMap::new();
user_map.insert(user_id1, "John Doe");

// Look up by string
let user = user_map.get(id_str);

// Use EntityId in a HashSet
let mut user_set = HashSet::new();
user_set.insert(user_id1);

// Check if a string is in the set
let contains = user_set.contains(id_str);

Usage

Basic Example with UUID

use entid::{EntityId, Prefix, UuidIdentifier, UuidEntityId};

type UserId = UuidEntityId::<User>;

// Define your entity types with custom prefixes
struct User;
impl Prefix for User {
    fn prefix() -> &'static str {
        "user"
    }

    fn delimiter() -> &'static str {
        "_"
    }
}

type PostId = EntityId::<Post, UuidIdentifier>;

struct Post;
impl Prefix for Post {
    fn prefix() -> &'static str {
        "post"
    }
    
    // Optional: Override the default delimiter
    fn delimiter() -> &'static str {
        "-"
    }
}

fn main() {
    // Generate random IDs with UUID
    let user_id = UserId::generate();
    let post_id = PostId::generate();
    
    // Print the IDs
    println!("User ID: {}", user_id); // e.g., "user_6ba7b810-9dad-11d1-80b4-00c04fd430c8"
    println!("Post ID: {}", post_id); // e.g., "post-123e4567-e89b-12d3-a456-426614174000"
    
    // Parse existing IDs
    let parsed_user_id = UserId::new("user_6ba7b810-9dad-11d1-80b4-00c04fd430c8").unwrap();
    
    // Type safety prevents mixing different entity IDs
    // This won't compile:
    // let wrong: UuidEntityId<Post> = user_id;
}

Using the Derive Macro

With the derive feature enabled, you can use the derive macro to implement the Prefix trait:

use entid::{Prefix, UuidEntityId, UlidEntityId};

type UserId = UuidEntityId::<User>;

#[derive(Prefix)]
#[entid(prefix = "user", delimiter = "_")]
struct User;

type PostId = UlidEntityId::<Post>;

#[derive(Prefix)]
#[entid(prefix = "post", delimiter = "-")]
struct Post;

type CommentId = UuidEntityId::<Comment>;

// The delimiter is optional and defaults to "_"
#[derive(Prefix)]
#[entid(prefix = "comment")]
struct Comment;

fn main() {
    let user_id = UserId::generate();
    println!("User ID: {}", user_id); // e.g., "user_6ba7b810-9dad-11d1-80b4-00c04fd430c8"
    
    let post_id = PostId::generate();
    println!("Post ID: {}", post_id); // e.g., "post-01H1VECZJYJ1QV2V0D0000JJDX"
    
    let comment_id = CommentId::generate();
    println!("Comment ID: {}", comment_id); // e.g., "comment_6ba7b810-9dad-11d1-80b4-00c04fd430c8"
}

Using ULID Instead of UUID

use entid::{EntityId, Prefix, UlidIdentifier, UlidEntityId};

type ProductId = UlidEntityId::<Product>;

struct Product;
impl Prefix for Product {
    fn prefix() -> &'static str {
        "prod"
    }
}

fn main() {
    // Generate a ULID-based ID
    let product_id = ProductId::generate();
    
    // ULIDs are lexicographically sortable by creation time
    let product_ids: Vec<UProductId> = (0..10)
        .map(|_| ProductId::generate())
        .collect();
    
    // Sorting will order by creation time
    let mut sorted_ids = product_ids.clone();
    sorted_ids.sort();
    
    // Get the timestamp from a ULID (not available with UUID)
    if let Some(timestamp_ms) = product_id.timestamp_ms() {
        println!("Product ID created at: {} ms since epoch", timestamp_ms);
    }
}

Using Deterministic UUIDs (v5)

use entid::{EntityId, Prefix, UuidIdentifier, Uuid};

type ApiKeyToken = EntityId::<ApiKey, UuidIdentifier>;

struct ApiKey;
impl Prefix for ApiKey {
    fn prefix() -> &'static str {
        "key"
    }
}

fn main() {
    // Create a namespace for your application
    let namespace = Uuid::parse_str("6ba7b810-9dad-11d1-80b4-00c04fd430c8").unwrap();
    
    // Create a UUID v5 identifier
    let uuid_id = UuidIdentifier::new_v5(&namespace, "user@example.com");
    
    // Create an entity ID from the identifier
    let api_key = ApiKeyToken::from_identifier(uuid_id);
    
    // Same input produces the same ID
    let uuid_id2 = UuidIdentifier::new_v5(&namespace, "user@example.com");
    let api_key2 = ApiKeyToken::from_identifier(uuid_id2);
    
    assert_eq!(api_key, api_key2);
}

Error Handling

use entid::{EntityId, EntityIdError, IdentifierError, Prefix, UuidIdentifier};

type UserId = <User, UuidIdentifier>;

struct User;
impl Prefix for User {
    fn prefix() -> &'static str {
        "user"
    }
}

fn parse_id(input: &str) -> Result<(), Box<dyn std::error::Error>> {
    // Parse an entity ID string
    match EntityId::UserId::new(input) {
        Ok(id) => {
            println!("Successfully parsed ID: {}", id);
            Ok(())
        },
        Err(EntityIdError::InvalidFormat) => {
            // Handle invalid format (missing prefix or delimiter)
            println!("Invalid ID format: {}", input);
            Err(Box::new(EntityIdError::InvalidFormat))
        },
        Err(EntityIdError::InvalidIdentifier) => {
            // Handle invalid identifier (not a valid UUID/ULID)
            println!("Invalid identifier part in ID: {}", input);
            Err(Box::new(EntityIdError::InvalidIdentifier))
        }
    }
}

// Parse a raw identifier string
fn parse_raw_identifier(input: &str) -> Result<UuidIdentifier, IdentifierError> {
    UuidIdentifier::parse(input)
}

Using with Serde

use entid::{EntityId, Prefix, UlidIdentifier};
use serde::{Serialize, Deserialize};

struct Order;
impl Prefix for Order {
    fn prefix() -> &'static str {
        "order"
    }
}

type OrderRecordId = EntityId<Order, UlidIdentifier>;

#[derive(Serialize, Deserialize)]
struct OrderRecord {
    id: OrderRecordId,
    customer_name: String,
    amount: f64,
}

fn main() {
    let order = OrderRecord {
        id: OrderRecordId::generate(),
        customer_name: "John Doe".to_string(),
        amount: 123.45,
    };
    
    // Serialize to JSON
    let json = serde_json::to_string(&order).unwrap();
    println!("JSON: {}", json);
    
    // Deserialize from JSON
    let deserialized: OrderRecord = serde_json::from_str(&json).unwrap();
    assert_eq!(order.id, deserialized.id);
}

Using with Databases

use entid::{EntityId, Prefix, UuidIdentifier};

type CustomerId = EntityId<Customer, UuidIdentifier>;

struct Customer;
impl Prefix for Customer {
    fn prefix() -> &'static str {
        "cust"
    }
}

// Example with a hypothetical database library
fn store_in_db(customer_id: &CustomerId, name: &str) {
    // The ID will be stored as a string like "cust_123e4567-e89b-12d3-a456-426614174000"
    let id_str = customer_id.as_str();
    
    // You can also access the raw identifier if needed
    let uuid = customer_id.identifier().uuid();
    
    // Database operations...
}

fn retrieve_from_db(id_str: &str) -> Result<CustomerId, entid::EntityIdError> {
    // Parse the ID string back into an EntityId
    CustomerId::new(id_str)
}

Advanced Usage

Creating Monotonic ULIDs

use entid::{EntityId, Prefix, UlidIdentifier};

type TaskId = EntityId::<Task, UlidIdentifier>;

struct Task;
impl Prefix for Task {
    fn prefix() -> &'static str {
        "task"
    }
}

fn main() {
    // Create a ULID-based entity ID
    let task1 = TaskId::generate();
    
    // Create a monotonic ULID (ensures ordering even within the same millisecond)
    let ulid2 = UlidIdentifier::monotonic_from(Some(task1.identifier()));
    let task2 = TaskId::from_identifier(ulid2);
    
    // task2 is guaranteed to sort after task1
    assert!(task2 > task1);
}

Custom Validation

use entid::{EntityId, Prefix, UuidIdentifier};

type ApiKeyToken = EntityId<ApiKey, UuidIdentifier>;

struct ApiKey;
impl Prefix for ApiKey {
    fn prefix() -> &'static str {
        "token"
    }
}

// Extend EntityId with custom validation logic
impl ApiKeyToken {
    pub fn is_valid_for_environment(&self, env: &str) -> bool {
        // Custom validation logic based on the UUID version
        match env {
            "production" => self.identifier().version() == Some(uuid::Version::Sha1),
            _ => true,
        }
    }
}

Choosing Between UUID and ULID

UUID Advantages

• Industry standard with wide adoption
• Multiple versions for different use cases (v1, v3, v4, v5)
• Well-supported in databases and other systems

ULID Advantages

• Lexicographically sortable (sorts by creation time)
• URL-safe (no special characters)
• Shorter string representation (26 characters vs 36 for UUID)
• Built-in timestamp component

Performance Considerations

• String representations are cached using OnceLock for thread-safe lazy initialization
• The EntityId type implements Hash, PartialEq, and Eq for efficient use in collections
• Memory usage is optimized by using PhantomData for type parameters

License

This project is licensed under the MIT License - see the LICENSE file for details.

Simplified API for Web Applications

The new parsing methods make it easier to work with IDs in web applications:

use entid::{Prefix, UuidEntityId};
use axum::{extract::Path, http::StatusCode, response::IntoResponse, Json};
use serde::{Deserialize, Serialize};

#[derive(Prefix)]
#[entid(prefix = "user")]
struct User;

type UserId = UuidEntityId<User>;

// Extract and validate a user ID from a URL path parameter
async fn get_user(Path(user_id_str): Path<String>) -> impl IntoResponse {
    // Parse the raw UUID string (without prefix) directly
    let user_id = match UserId::from_raw_str(&user_id_str) {
        Ok(id) => id,
        Err(_) => return (StatusCode::BAD_REQUEST, "Invalid user ID").into_response(),
    };

    // Fetch user from database using the ID...
    let user = fetch_user(user_id).await?;
    
    (StatusCode::OK, Json(user)).into_response()
}

// Parse an ID with custom error handling for better API responses
async fn update_user(
    Path(user_id_str): Path<String>,
    Json(payload): Json<UserUpdatePayload>,
) -> impl IntoResponse {
    // Use parse_raw_str with custom error handling
    let user_id = match UserId::parse_raw_str(user_id_str, |e| {
        (StatusCode::BAD_REQUEST, format!("Invalid user ID: {}", e))
    }) {
        Ok(id) => id,
        Err(err) => return err.into_response(),
    };

    // Update user in database...
    update_user_in_db(user_id, payload).await?;
    
    StatusCode::NO_CONTENT.into_response()
}

Working with External Systems

When integrating with external systems, you often need to convert between different ID formats:

use entid::{Prefix, UuidEntityId, UlidEntityId};

#[derive(Prefix)]
#[entid(prefix = "user")]
struct User;

#[derive(Prefix)]
#[entid(prefix = "order")]
struct Order;

type UserId = UuidEntityId<User>;
type OrderId = UlidEntityId<Order>;

// Convert from an external system's user ID to our internal format
fn import_external_user(external_id: &str) -> Result<UserId, String> {
    // The external system uses raw UUIDs without prefixes
    UserId::from_raw_str(external_id)
        .map_err(|e| format!("Failed to import user: {}", e))
}

// Export our internal ID to a format the external system expects
fn export_order_to_external_system(order_id: &OrderId) -> String {
    // The external system needs just the ULID part without our prefix
    order_id.id_str().to_string()
}

// Convert a batch of IDs from an external system
fn import_user_batch(external_ids: &[String]) -> Vec<UserId> {
    external_ids
        .iter()
        .filter_map(|id| UserId::from_raw_str(id).ok())
        .collect()
}

Choosing Between UUID and ULID

UUID Advantages

• Industry standard with wide adoption
• Multiple versions for different use cases (v1, v3, v4, v5)
• Well-supported in databases and other systems

ULID Advantages

• Lexicographically sortable (sorts by creation time)
• URL-safe (no special characters)
• Shorter string representation (26 characters vs 36 for UUID)
• Built-in timestamp component

Performance Considerations

• String representations are cached using OnceLock for thread-safe lazy initialization
• The EntityId type implements Hash, PartialEq, and Eq for efficient use in collections
• Memory usage is optimized by using PhantomData for type parameters

License

This project is licensed under the MIT License - see the LICENSE file for details.