Use CocoaPods in your project

1. Open the iOSConferences/Model/Data.swift file.

2. Delete unnecessary code: the loadFile(_:) method and the conferencesData variable.

3. Add a new class named ConferencesLoader and declare its conformance to ObservableObject:

   public class ConferencesLoader: ObservableObject { }

4. In the new class, add a @Published property conferences that stores an array of the Conference objects:

   public class ConferencesLoader: ObservableObject { @Published var conferences = [Conference]() }

5. Add the loadConferences() method that you'll implement later.

   public class ConferencesLoader: ObservableObject { @Published var conferences = [Conference]() func loadConferences() { } }

6. Add an initializer for the class: while the caret is inside the class code, click ⌘ N, select Initializer, and choose Select none in the dialog that opens. Add the loadConferences() method to the initializer:

   public class ConferencesLoader: ObservableObject { @Published var conferences = [Conference]() public init() { loadConferences() } func loadConferences() { } }

1. In the loadConferences() method, call URLSession.shared.dataTaskPublisher(for:):

   func loadConferences() { URLSession.shared.dataTaskPublisher(for: url) }

2. With the caret placed at url, press ⌥ ⏎ and select Create global variable 'url'. This intention action will let you introduce the global variable directly from its usage.

3. Set the link to the remote YAML file as the variable's value:

   let url = URL(string: "https://raw.githubusercontent.com/Lascorbe/CocoaConferences/master/_data/conferences.yml") public class ConferencesLoader: ObservableObject { // ... }

4. You will see that the url parameter is highlighted red — press ⌥ ⏎ to check available options for fixing it. Select Force-unwrap using '!'..., which will add the ! character after the url variable usage:

   func loadConferences() { URLSession.shared.dataTaskPublisher(for: url!) }

1. In the Data.swift file, import the Yams framework:

   import Yams

2. Call the decode(_:from:) method for the created publisher and pass the [Conference] type and YAMLDecoder as the method parameters:

   func loadConferences() { URLSession.shared.dataTaskPublisher(for: url!) .decode(type: [Conference].self, decoder: YAMLDecoder()) }

   YAMLDecoder is highlighted red. Hover over the highlighted code to see the error message:

   Argument type 'YAMLDecoder' does not conform to expected type 'TopLevelDecoder'

   This means you need to create an extension for the YAMLDecoder which will conform to the TopLevelDecoder type.

3. Import the Combine framework where the TopLevelDecoder type belongs to:

   import Yams import Combine

4. Add an extension of the YAMLDecoder type and declare its conformance to TopLevelDecoder:

   let url = URL(string: "https://raw.githubusercontent.com/Lascorbe/CocoaConferences/master/_data/conferences.yml") extension YAMLDecoder: TopLevelDecoder { } public class ConferencesLoader: ObservableObject { // ... }

5. The TopLevelDecoder protocol requires the conforming types to provide the Input property and the decode(_:from:) method.

   To add the required property and method, you can use the corresponding code intention:

   place the caret at extension, press ⌥ ⏎, select Do you want to add protocol stubs?, and click ⏎. This will add a code stub for the Input typealias:

   extension YAMLDecoder: TopLevelDecoder { public typealias Input = type }

   Specify the URLSession.DataTaskPublisher.Output data type here:

   public typealias Input = URLSession.DataTaskPublisher.Output

   Again, place the caret at extension, press ⌥ ⏎, select Do you want to add protocol stubs?, and click ⏎. This time, AppCode adds the decode(_:from:) method stub code:

   public func decode <T>(_ type: T.Type, from: URLSession.DataTaskPublisher.Output) throws -> T where T : Decodable { <#code#> }

   Add the method's implementation:

   public func decode<T:Decodable>(_ type: T.Type, from data: Input) throws -> T { try decode(type, from: String(data: data.data, encoding: .utf8)!) }

As a result, the YAMLDecoder extension looks this way:

1. Get back to the loadConferences() method of the ConferencesLoader class and in the receive(on:) method, specify a scheduler on which the current publisher is going to receive elements:

   func loadConferences() { URLSession.shared.dataTaskPublisher(for: url!) .decode(type: [Conference].self, decoder: YAMLDecoder()) .receive(on: RunLoop.main) }

2. Use the eraseToAnyPublisher() method to erase the publisher's actual type and convert it to AnyPublisher:

   func loadConferences() { URLSession.shared.dataTaskPublisher(for: url!) .decode(type: [Conference].self, decoder: YAMLDecoder()) .receive(on: RunLoop.main) .eraseToAnyPublisher() }

3. Add the completion parameter to the loadConferences() method's declaration:

   func loadConferences(completion: @escaping ([Conference]) -> Void) { // ... }

4. With the sink(receiveCompletion:receiveValue:) method, attach a subscriber to the publisher. In the receiveCompletion parameter, pass a closure to execute on completion — here you can specify how to handle the errors. In the receiveValue parameter, pass a closure to execute when receiving a value.

   func loadConferences(completion: @escaping ([Conference]) -> Void) { URLSession.shared.dataTaskPublisher(for: url!) .decode(type: [Conference].self, decoder: YAMLDecoder()) .receive(on: RunLoop.main) .eraseToAnyPublisher() .sink(receiveCompletion: { completion in switch completion { case .finished: break case .failure(let error): print(error.localizedDescription) } }, receiveValue: { conferences in completion(conferences) }) }

5. Put the result of the URL session to a separate variable. With the caret placed inside the loadConferences() method, press ⌃ ⌥ V, select the whole statement in the dropdown list that opens, and press ⏎. Name the variable as result, select the Declare with var and Specify type explicitly checkboxes, and press ⏎ twice:

   

6. Move the variable declaration to the class level. With the caret placed at the variable line, press ⌥ ⏎ and select Split into declaration and assignment:

   

   Add ? to the AnyCancellable type to make it optional and place the result variable declaration right below the @Published var conferences = [Conference]() line:

   public class ConferencesLoader: ObservableObject { @Published var conferences = [Conference]() var result: AnyCancellable? }

7. In the initializer where the loadConferences() method is called, pass the closure expression as the method's parameter:

   public init() { loadConferences(completion: { conferences in self.conferences = conferences }) }

8. You can also simplify the method's call by using the trailing closure syntax:

   public init() { loadConferences() { conferences in self.conferences = conferences } }