Networking (URLSession + async/await)

Relax. We'll talk through this in plain words — no textbook voice.

What you'll walk away with

Understand Networking (URLSession + async/await) with nothing to be intimidated by
Get comfortable running Xcode/SwiftUI code yourself
Be able to apply this concept in a real project right away

Let's think about it this way for a second

`URLSession` is iOS's built-in networking API (no need for a third-party library like Android's Retrofit — Apple provides it for you). In modern Swift (5.5+), combining it with `async`/`await` syntax is easier to read than callback-based code (`completion handler`) — `URLSession.shared.data(from: url)` is an `async` function, called with `try await`. You can decode the JSON response into a struct that conforms to `Codable` using `JSONDecoder`.

Let's connect this to a real-world scenario

If you define `struct WeatherResponse: Codable { let city: String; let tempCelsius: Double }` and write `func fetchWeather(city: String) async throws -> WeatherResponse { let url = URL(string: "https://api.example.com/weather?city=\(city)")!; let (data, _) = try await URLSession.shared.data(from: url); return try JSONDecoder().decode(WeatherResponse.self, from: data) }` — calling `Task { weather = try await fetchWeather(city: "Yangon") }` fetches the weather data from the API and displays it in your UI.

URLSession = iOS's built-in networking API (no third-party library needed)
async/await = modern Swift Concurrency syntax that's easier to read than callback-based code
Codable protocol + JSONDecoder = decode a JSON response into a Swift struct

Let's look at it together

swift

struct WeatherResponse: Codable {
    let city: String
    let tempCelsius: Double
}

func fetchWeather(city: String) async throws -> WeatherResponse {
    let url = URL(string: "https://api.example.com/weather?city=\(city)")!
    let (data, _) = try await URLSession.shared.data(from: url)
    return try JSONDecoder().decode(WeatherResponse.self, from: data)
}

You should see

$ let weather = try await fetchWeather(city: "Yangon")
// weather: WeatherResponse(city: "Yangon", tempCelsius: 32.0)

5-minute try-it

Try defining your own `fetchWeather` function (pick any free public weather API), and design the `try await` calling pattern inside a `Task { }`.

A quick heads-up

If you hardcode an API key (secret) in your app code, it ends up in the app bundle and can be extracted by decompiling it — sensitive keys should be routed through a backend proxy server instead.

Easy traps

Trying to call `URLSession.shared.data(from:)` without `await` — this is a compile error (it's an async function, so await is required)
Only writing the success case and not handling the error case (network down, invalid JSON) of an API call — you need to add error handling with `try`/`catch`

Now try it yourself

Try defining your own `fetchWeather` function (pick any free public weather API), and design the `try await` calling pattern inside a `Task { }`.

You'll know it worked when: $ let weather = try await fetchWeather(city: "Yangon") // weather: WeatherResponse(city: "Yangon", tempCelsius: 32.0)