SwiftIdentifier

A lightweight library that helps to define ID types.

Requirements

Swift 5.4+

Features

What problems does SwiftIdentifier solve?

Suppose you have User and Book types, each of which has an ID of type Int:

struct User {
    let id: Int
}

struct Book {
    let id: Int
}

and have a userIDHandler closure:

let userIDHandler: (Int) -> Void = { ... }

There are two main problems here.

userIDHandler accepts a Book ID, leading to silent bugs.
The argument type of userIDHandler does not fully convey intent.

Solution with SwiftIdentifier

You can easily define different ID types for each type!

struct User {
    typealias ID = Identifier<Self, Int>
    let id: ID
}
struct Book {
    typealias ID = Identifier<Self, Int>
    let id: ID
}

let user = User(id: 10)
let book = Book(id: 500)

// The argument type become clearer!
let userIDHandler: (User.ID) -> Void = { ... }

userIDHandler(user.id) // OK
userIDHandler(book.id) // Compile error!

Other features

You can collaborate nicely with Codable.

struct User: Codable {
    typealias ID = Identifier<Self, Int>
    let id: ID
    let name: String
}

// Compatible JSON
"""
{
    "id": 100,
    "name": "John"
}
"""

Using SwiftIdentifier in your project

To use the SwiftIdentifier library in a SwiftPM project, add the following line to the dependencies in your Package.swift file:

.package(url: "https://github.com/jrsaruo/SwiftIdentifier", from: "1.1.1"),

and add SwiftIdentifier as a dependency for your target:

.target(name: "<target>", dependencies: [
    .product(name: "SwiftIdentifier", package: "SwiftIdentifier"),
    // other dependencies
]),

Finally, add import SwiftIdentifier in your source code.