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Since URLSession was introduced in iOS 7, third party libraries have somehow lesser value.

This post is a quick guide with snippets to some common use cases when working with HTTP APIs using the first party Foundation framework.

HTTP GET

let url = URL(string: "https://samwize.com/api/hero")!
let task = URLSession.shared.dataTask(with: url) { data, response, error in
    print(String(data: data!, encoding: .utf8))
}
task.resume()

Just that few lines of code to fetch from a URL.

The dataTask() method is a HTTP GET request.

HTTP POST

let url = URL(string: "https://samwize.com/api/hero")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
let payload = "id=1234".data(using: .utf8)!
let task = URLSession.shared.uploadTask(with: request, from: payload) { data, response, error in
    print(String(data: data!, encoding: .utf8))
}
task.resume()

The uploadTask() method is for a POST request. Or you may change the httpMethod to UPDATE etc.

POST with query string

The POST request above is a simple example, with a payload that doesn’t require any percent encoding. But it is more likely that you have longer query items.

URLQueryItem (also Foundation framework) provides a basic struct for constructing key-value pairs.

Together with URLComponents, you can add as many key-value pairs to a URLComponents, then access the percentEncodedQuery.

var urlComponents = URLComponents()
let q1 = URLQueryItem(name: "name", value: "with space that needs encoding")
urlComponents.queryItems = [q1]
let payload = urlComponents.percentEncodedQuery!.data(using: .utf8)

Codable Model

New in Swift 4, JSON can be decoded to a struct easily,

I have a separate guide to Codable struct.

Let’s say in the POST API, a Hero object in JSON is returned, we could decode it easily.

let task = URLSession.shared.uploadTask(with: request, from: payload) { data, response, error in
    let decoder = JSONDecoder()
    let hero = try! decoder.decode(Hero.self, from: data!)
}

Similarly, you can encode a model, then POST the JSON string/data as a payload.

Other Resources

Apple’s official guide on URL Loading System and how to fetch data is their guide to the networking framework. You could use URLSessionConfiguration to configure your own session, and also use URLSessionDelegate for a delegate pattern to receive the data.