Making Network Requests in Swift: 3 Practical Examples

Introduction to Making Network Requests in Swift

Making network requests in Swift is a fundamental skill for iOS developers. Whether you’re fetching data from a web API or sending user information to a server, understanding how to perform these requests is crucial. In this article, we’ll explore three diverse examples of making network requests in Swift, covering different scenarios to help you grasp the concept effectively.

Example 1: Fetching JSON Data from a Public API

In this example, we will fetch JSON data from a public API, specifically the JSONPlaceholder API, which provides fake data for testing and prototyping.

This is a common use case when you want to retrieve data to display in your app, such as user information or posts.

import Foundation

struct Post: Codable {
    let userId: Int
    let id: Int
    let title: String
    let body: String
}

func fetchPosts() {
    let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!
    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        if let error = error {
            print("Error fetching posts: \(error)")
            return
        }

        guard let data = data else {
            print("No data returned")
            return
        }

        do {
            let posts = try JSONDecoder().decode([Post].self, from: data)
            print(posts)
        } catch {
            print("Error decoding JSON: \(error)")
        }
    }

    task.resume()
}

fetchPosts()

Notes

• Ensure you have the correct URL to fetch data.
• The Post struct conforms to Codable, making it easier to decode JSON data into Swift objects.

Example 2: Sending Data with a POST Request

In this example, we will demonstrate how to send data to a server using a POST request. This is useful when you need to submit user data, such as form submissions.

We’ll use the same JSONPlaceholder API to simulate sending a new post.

import Foundation

struct NewPost: Codable {
    let title: String
    let body: String
    let userId: Int
}

func createPost() {
    let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")

    let newPost = NewPost(title: "New Post Title", body: "This is the body of the new post", userId: 1)

    do {
        let jsonData = try JSONEncoder().encode(newPost)
        request.httpBody = jsonData
    } catch {
        print("Error encoding JSON: \(error)")
        return
    }

    let task = URLSession.shared.dataTask(with: request) { data, response, error in
        if let error = error {
            print("Error creating post: \(error)")
            return
        }

        guard let data = data else {
            print("No data returned")
            return
        }

        do {
            let createdPost = try JSONDecoder().decode(NewPost.self, from: data)
            print(createdPost)
        } catch {
            print("Error decoding JSON: \(error)")
        }
    }

    task.resume()
}

createPost()

Notes

• Always set the httpMethod in your request to indicate the type of request you are making.
• Use URLRequest to customize your request (such as adding headers).

Example 3: Handling Errors and Responses Gracefully

In this example, we will focus on how to handle different types of errors and responses when making network requests. This is crucial for providing a good user experience.

This example will fetch data and handle potential errors such as network issues or invalid responses.

import Foundation

func fetchUser() {
    let url = URL(string: "https://jsonplaceholder.typicode.com/users/1")!
    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        if let error = error {
            print("Network error: \(error.localizedDescription)")
            return
        }

        guard let httpResponse = response as? HTTPURLResponse else {
            print("Invalid response")
            return
        }

        guard (200...299).contains(httpResponse.statusCode) else {
            print("Server error: \(httpResponse.statusCode)")
            return
        }

        guard let data = data else {
            print("No data returned")
            return
        }

        do {
            let user = try JSONDecoder().decode(User.self, from: data)
            print(user)
        } catch {
            print("Error decoding JSON: \(error)")
        }
    }

    task.resume()
}

fetchUser()

Notes

• Always check for errors and handle them gracefully to improve user experience.
• Use HTTPURLResponse to get the status code and verify that the request was successful.

By following these examples of making network requests in Swift, you should feel more confident in handling data retrieval and submission in your iOS applications. Happy coding!