iOSアプリ設計パターン入門 第3章サンプルコード

iOS_architecture_03.swift

protocol MessageSenderDelegate {
    func stateの変化を伝える()
}

protocol Message {
}
protocol MessageInput {
    associatedtype Payload
    func validate() throws -> Payload
}
protocol MessageSenderAPI {
    associatedtype Payload
    associatedtype Response: Message
    func send(payload: Payload, completion: @escaping (Response?) -> Void)
}
final class MessageSender<API: MessageSenderAPI, Input: MessageInput>
where API.Payload == Input.Payload {
    var delegate: MessageSenderDelegate?

    let api: API
    var input: Input {
        didSet { state = State(evaluating: input) }
    }
    enum State {
        case inputting(validationError: Error?)
        case sending
        case sent(API.Response)
        case connectionFailed

        init(evaluating input: Input) {
            do {
                try input.validate()
                self = .inputting(validationError: nil)
            } catch let e {
                self = .inputting(validationError: e)
            }
        }
        mutating func accept(response: API.Response?) {
            self = response.map(State.sent) ?? .connectionFailed
        }
    }
    private(set) var state: State {
        didSet { delegate?.stateの変化を伝える() }
    }
    init(api: API, input: Input) {
        self.api = api
        self.input = input
        self.state = State(evaluating: input)
    }
    func send() {
        do {
            let payload = try input.validate()
            state = .sending
            api.send(payload: payload) { [weak self] in
                self?.state.accept(response: $0)
            }
        } catch let e {
            state = .inputting(validationError: e)
        }
    }
}

enum ImageMessageInputError: Error {
    case noImage, tooLongText(count: Int)
}
struct ImageMessageInput: MessageInput {
    var text: String?
    var image: UIImage?
    func validate() throws -> (text: String?, image: UIImage) {
        guard let image = image
            else { throw ImageMessageInputError.noImage }
        if let text = text, text.count >= 80
            { throw ImageMessageInputError.tooLongText(count: text.count) }
        return (text, image)
    }
}
struct ImageMessage: Message {
    let id: Int
    let text: String?
    let imageURL: URL
}
final class ImageMessageSenderAPI: MessageSenderAPI {
    var successes: Bool = true
    func send(payload: (text: String?, image: UIImage), completion: @escaping (ImageMessage?) -> Void) {
        if successes {
            completion(ImageMessage(id: 1, text: payload.text, imageURL: URL(string: "localhost://")!))
        } else {
            completion(nil)
        }
    }
}

let api = ImageMessageSenderAPI()
let sender = MessageSender(
    api: api,
    input: ImageMessageInput(text: nil, image: nil)
)

class SpyMessageSenderDelegate: MessageSenderDelegate {
    func stateの変化を伝える() {
        print(sender.state)
    }
}

sender.delegate = SpyMessageSenderDelegate()

sender.input.text = String(repeating: "あ", count: 100)
sender.input.image = nil
sender.send()

sender.input.image = UIImage()
sender.send()

sender.input.text = "ほげほげ"

api.successes = false
sender.send()

sender.send()

api.successes = true
sender.send()

/*
 inputting(validationError: Optional(__lldb_expr_15.ImageMessageInputError.noImage))
 inputting(validationError: Optional(__lldb_expr_15.ImageMessageInputError.noImage))
 inputting(validationError: Optional(__lldb_expr_15.ImageMessageInputError.noImage))
 inputting(validationError: Optional(__lldb_expr_15.ImageMessageInputError.tooLongText(count: 100)))
 inputting(validationError: Optional(__lldb_expr_15.ImageMessageInputError.tooLongText(count: 100)))
 inputting(validationError: nil)
 sending
 connectionFailed
 sending
 connectionFailed
 sending
 sent(__lldb_expr_15.ImageMessage(id: 1, text: Optional("ほげほげ"), imageURL: localhost://))
 */