Swift cat images

README.md

Get a random cat image:

Cats.getRandomImageURL { url in
    
}

Set a random cat image on UIImageView:

imageView.setRandomCatImage()

Cats.swift

enum Cats {
    private struct CatResponse: Decodable {
        let url: URL
    }
    
    @discardableResult
    static func getRandomImageURL(completion: @escaping (URL?) -> Void) -> URLSessionDataTask {
        let request = URLRequest(url: URL(string: "https://api.thecatapi.com/v1/images/search")!)
        let task = URLSession.shared.dataTask(with: request) { data, _, _ in
            let catURL: URL? = {
                guard let data = data,
                      let cats = try? JSONDecoder().decode([CatResponse].self, from: data),
                      let firstCat = cats.first
                else { return nil }
                return firstCat.url
            }()
            
            DispatchQueue.main.async {
                completion(catURL)
            }
        }
        task.resume()
        return task
    }
    
    @discardableResult
    static func image(url: URL, completion: @escaping (UIImage?) -> Void) -> URLSessionDataTask {
        let task = URLSession.shared.dataTask(with: url) { data, _, _ in
            let image: UIImage? = {
                guard let data = data else { return nil }
                return UIImage(data: data)
            }()
            
            DispatchQueue.main.async {
                completion(image)
            }
        }
        task.resume()
        return task
    }
}

UIImageView+Cats.swift

extension UIImageView {
    func setRandomCatImage(placeholder: UIImage? = nil, emptyImage: UIImage? = nil) {
        activeCatRequest?.cancel()
        image = placeholder
        activeCatRequest = Cats.getRandomImageURL { [weak self] url in
            switch url {
            case let .some(url):
                self?.setCatImage(url: url, emptyImage: emptyImage)
                
            case .none:
                self?.image = emptyImage
            }
        }
    }
    
    private func setCatImage(url: URL, emptyImage: UIImage?) {
        activeCatRequest = Cats.image(url: url) { [weak self] image in
            switch image {
            case let .some(image):
                self?.image = image
                
            case .none:
                self?.image = emptyImage
            }
        }
    }
}

private extension UIImageView {
    struct AssociatedKeys {
        static var activeCatRequest = "ActiveCatRequest"
    }
    
    var activeCatRequest: URLSessionDataTask? {
        get {
            objc_getAssociatedObject(self, &AssociatedKeys.activeCatRequest) as? URLSessionDataTask
        }
        set {
            objc_setAssociatedObject(self, &AssociatedKeys.activeCatRequest, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
}