Networking-in-iOS-Terminology.md

Networking in iOS (Terminology)

1. JSON - web api formatted data the is the most popular way of serving downloaded or uploaded content from a network resource

   {
     "language": "swift", 
     "releaseYear": 2014, 
     "url": "https://developer.apple.com/swift/images/swift-og.png"
   }

2. Codable (Decodable, Encodable) - introduced in Swift 4.2 this protocol allows us to convert JSON into Swift objects quite easily compared to its predecessor JSONSerialization

   struct ProgrammingLanguage: Codable {
     let language: String 
     let releaseYear: Int
     let url: String
   }

3. JSONDecoder() - class that converts JSON data to a swift object. The swift object must conform to the Codable protocol.

   let headlinesData = try JSONDecoder().decode(HeadlinesData.self, from: data)

4. URL - a path to a local or network resource

   URL(string: urlStirng)

5. URLSession - class used to initiate a network request for a resource, used to upload or download web content

   let dataTask = URLSession.shared.dataTask(with: url) { (data, response, error) in
     // code here
   }
   dataTask.resume()
    

6. Result type - an enum that is used in a completion handler when making a network request. The enum cases are success and failure.

   (Result<UIImage?, Error>) -> ()

7. Grand Central Dispatch (GCD) - the concurrency API in Swift. Concurrency is the act of many things happening simultaneously. e.g in iOS that would be allowing a table view to be scrolled without interruption to the user of the application while images are being fetched from the network.

   DispatchQueue.main.async {
     // UI updates go here
     self.headlineImageView.image = image
   }

8. Escaping Closures - a completion handler needs to be marked @escaping due to the fact that the function returns before the closure value is set from typically an asychronous call (example a background task from fetching a network resource)

   completion: @escaping (Result<UIImage?, Error>) -> ()

9. Capture list - [weak self] or [unowned self] - used to break retain cycles. Having a retain cycle leads to memory leaks and eventual crashes in our applications.

   { [unowned self] (result) in
      // code 
   }

10. RESTFul API - uses http methods e.g POST, GET, PUT, DELETE to communicate with a web API (Application Programming Interface). Below is an example of an endpoint from the itunes search RESTFul API performing a GET request to retrieve podcast with the term being "swift" GET https://itunes.apple.com/search?media=podcast&limit=200&term=swift

...more to come