GraphQL API with Swift: Step-by-Step Tutorial for iOS and macOS

Introduction: Why GraphQL and Swift?

Modern iOS and macOS development requires flexible and efficient ways to interact with the server. Traditional REST APIs often lead to the problem of over-fetching (retrieving unnecessary data) or under-fetching (insufficient data). GraphQL solves these problems by allowing the client to request only the data it needs in a single query.

In this tutorial, we will create a full-fledged Swift application that interacts with a GraphQL API. You will learn how to set up the project, execute queries, mutations, and handle errors. As a client, we will use Apollo iOS — the most popular library for working with GraphQL in the Apple ecosystem.

Project Setup and Installing Apollo iOS

Creating a New Project

Open Xcode and create a new iOS or macOS App project. Let's name it GraphQLDemo.

Installing Apollo iOS via Swift Package Manager

1. In Xcode, go to File → Add Packages...
2. Paste the Apollo repository URL: https://github.com/apollographql/apollo-ios.git
3. Select the latest stable version and click Add Package.
4. Make sure the package is added to your app's target.

Code Generation from GraphQL Schema

Apollo uses code generation to create type-safe classes. For this, we need a schema file (schema.graphqls) and query files (.graphql).

Create a GraphQL folder in the project and place the following there:

• schema.graphqls — download your API's schema or use a public one (e.g., Countries GraphQL API).
• Queries.graphql — a file with your queries.

Example content of Queries.graphql:

query GetCountries {  countries {    code    name    capital    currency  }}

Now add a Build Phase for code generation. In Xcode: Target → Build Phases → + → New Run Script Phase. Paste the script:

cd "${SRCROOT}/${TARGET_NAME}"./Pods/Apollo/scripts/run-bundled-codegen.sh codegen:generate --target=swift --includes=./**/*.graphql --localSchemaFile=./schema.graphqls ./GraphQL/API.swift

Note: In modern versions of Apollo iOS, apollo-ios-cli is used. We recommend checking the official documentation for up-to-date instructions.

Executing GraphQL Queries

Initializing the Apollo Client

Let's create a manager for working with Apollo. Open the file NetworkManager.swift:

import Foundationimport Apollo

class NetworkManager {    static let shared = NetworkManager()        private(set) lazy var apollo: ApolloClient = {        let url = URL(string: "https://countries.trevorblades.com/")!        return ApolloClient(url: url)    }()}

Executing a Query

Now let's execute the GetCountries query in our ViewController:

import UIKit

class ViewController: UIViewController {        override func viewDidLoad() {        super.viewDidLoad()        fetchCountries()    }        private func fetchCountries() {        NetworkManager.shared.apollo.fetch(query: GetCountriesQuery()) { result in            switch result {            case .success(let graphQLResult):                if let countries = graphQLResult.data?.countries {                    for country in countries {                        print("\\(country.name) - \\(country.capital ?? "N/A")")                    }