1. Introduction

In this tutorial, we will learn how to make network requests in Swift using URLSession. URLSession is a part of Foundation framework, and it makes the process of fetching, posting, and manipulating data from a server quite straightforward.

You will learn:
- How to use URLSession to make GET and POST requests
- How to parse JSON from a server
- Error handling in network requests

Prerequisites:
- Basic understanding of Swift programming language
- Familiarity with JSON and HTTP requests would be beneficial but not necessary

2. Step-by-Step Guide

The first step in making a network request is to create a URL. After creating the URL, we will build a URLSession to manage the data transfer from the web service.

GET Request

A GET request is a type of HTTP request that retrieves data from a server.

let url = URL(string: "https://api.example.com/data")

let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
    // handle the result here
}

task.resume()

In the above code:
- We first create a URL object.
- We then create a data task, which is a lightweight, unidirectional channel to a server.
- The task is then resumed. By default, tasks start in a suspended state.

POST Request

A POST request is another type of HTTP request that sends data to a server.

let parameters = ["param1": "value1", "param2": "value2"]
let url = URL(string: "https://api.example.com/data")
var request = URLRequest(url: url!)
request.httpMethod = "POST"
request.httpBody = try? JSONSerialization.data(withJSONObject: parameters, options: [])

let task = URLSession.shared.dataTask(with: request) {(data, response, error) in
    // handle the result here
}

task.resume()

In the above code, we specify the HTTP method as "POST" and set the request body to our parameters.

3. Code Examples

Example 1: GET Request

let url = URL(string: "https://api.example.com/data")

let task = URLSession.shared.dataTask(with: url!) {(data, response, error) in
    if let error = error {
        print("Error: \(error)")
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print("Received data:\n\(str!)")
    }
}

task.resume()

In this example, we send a GET request to a server and print out the received data. If an error occurs, we print out the error.

Example 2: POST Request

let parameters = ["username": "test", "password": "1234"]
let url = URL(string: "https://api.example.com/login")
var request = URLRequest(url: url!)
request.httpMethod = "POST"
request.httpBody = try? JSONSerialization.data(withJSONObject: parameters, options: [])

let task = URLSession.shared.dataTask(with: request) {(data, response, error) in
    if let error = error {
        print("Error: \(error)")
    } else if let data = data {
        let str = String(data: data, encoding: .utf8)
        print("Received data:\n\(str!)")
    }
}

task.resume()

In this example, we send a POST request to a login endpoint with a username and password. We then print the data received from the server.

4. Summary

In this tutorial, we learned how to make GET and POST network requests using URLSession in Swift. We also learned how to handle errors and parse JSON data.

Next steps:
- Learn more about URLSession and its capabilities
- Practice with different APIs and endpoints
- Learn about error handling and how to display error messages to the user

Additional resources:
- Apple's URLSession Documentation
- Apple's Networking Guide

5. Practice Exercises

1. Make a GET request to an API of your choice and print out the data received.
2. Make a POST request to an API of your choice. Send some data in the request body and print out the server's response.
3. Handle errors in your network requests. If an error occurs, print out a custom error message.

Remember, practice makes perfect. The more you work with URLSession and network requests, the more comfortable you'll become.