How to Write a REST API in Swift in 30 Minutes

Introduction: Why REST API on Swift is Fast and Modern

Developing mobile applications for iOS and macOS requires not only a beautiful interface but also a reliable server backend. REST API (Representational State Transfer) remains the de facto standard for data exchange between client and server. If you are already writing in Swift for the Apple ecosystem, creating an API in the same language is a logical step. This allows you to reuse data models, avoid code duplication, and implement changes faster.

In this article, we will show you how to write a full-fledged REST API in Swift using the Vapor framework — the most popular web framework for Swift. You will learn how to set up a project, create routes, handle JSON, and run the server. The entire process will take no more than 30 minutes. Ready? Let's go!

1. Environment Setup and Installing Vapor

Before writing code, make sure you have the necessary tools installed. Working with Vapor requires Swift 5.9 or newer (Swift 6 is recommended). You will also need a terminal and a code editor (Xcode or VS Code).

Installing Vapor Toolbox

Vapor Toolbox is a command-line utility that simplifies creating and managing projects. Install it via Homebrew:

brew install vapor

If Homebrew is not installed, download it from brew.sh. After installation, check the version:

vapor --version

Creating a New Project

Open the terminal and run the command:

vapor new MyAPI --template=api

The --template=api flag creates a basic structure for a REST API without unnecessary files. Navigate to the project folder:

cd MyAPI

Now open the project in Xcode:

open Package.swift

Or use any other editor. Done! You have a clean Vapor template.

2. Basic Structure: Models, Controllers, and Routes

Vapor uses the MVC (Model-View-Controller) architecture adapted for server-side development. We will create a simple API for managing a To-Do list.

Creating the Model

A model is a structure that describes the data. In the Sources/App/Models/ folder, create a file Todo.swift:

import Fluentimport Vapor

final class Todo: Model, Content {    static let schema = "todos"        @ID(key: .id)    var id: UUID?        @Field(key: "title")    var title: String        @Field(key: "is_completed")    var isCompleted: Bool        init() { }        init(id: UUID? = nil, title: String, isCompleted: Bool = false) {        self.id = id        self.title = title        self.isCompleted = isCompleted    }}

We use Fluent — Vapor's ORM for working with databases. The model is automatically serialized to JSON thanks to the Content protocol.

Creating the Controller

The controller contains the request handling logic. Create a file Sources/App/Controllers/TodoController.swift:

import Vaporimport Fluent

struct TodoController: RouteCollection {    func boot(routes: RoutesBuilder) throws {        let todos = routes.grouped("todos")        todos.get(use: index)        todos.post(use: create)        todos.group(":todoID") { todo in            todo.delete(use: delete)        }    }        // GET /todos — get all tasks    func index(req: Request) async throws -> [Todo] {        try await Todo.query(on: req.db).all()    }        // POST /todos — create a task    func create(req: Request) async throws -> Todo {        let todo = try req.content.decode(Todo.self)        try await todo.save(on: req.db)        return todo    }        // DELETE /todos/:id — delete a task    func delete(req: R