Kingfisher/Sources/SwiftUI/ImageBinder.swift

//
//  ImageBinder.swift
//  Kingfisher
//
//  Created by onevcat on 2019/06/27.
//
//  Copyright (c) 2019 Wei Wang <onevcat@gmail.com>
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.

import Combine
import SwiftUI

@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
extension KFImage {

    public class ImageBinder: BindableObject {
        let url: URL

        public var didChange = PassthroughSubject<KFCrossPlatformImage?, Never>()
        var subject = PassthroughSubject<RetrieveImageResult, KingfisherError>()
        var downloadTask: DownloadTask?

        var image: Kingfisher.KFCrossPlatformImage? {
            didSet { didChange.send(image) }
        }

        init(url: URL) {
            self.url = url
        }

        func start() {
            let source = Source.network(url)
            downloadTask = KingfisherManager.shared
                .retrieveImage(with: source) { [weak self] result in
                    guard let self = self else { return }

                    self.downloadTask = nil
                    switch result {
                    case .success(let value):
                        self.image = value.image
                        self.subject.send(value)
                        self.subject.send(completion: .finished)
                    case .failure(let error):
                        self.subject.send(completion: .failure(error))
                    }
                }
        }

        public func cancel() {
            downloadTask?.cancel()
        }
    }
}