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: "1.1.0"),

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.