将 URL 数组转换为 UIImage 数组

Question

我有一个链接到图像文件的URL数组，如何将它们存储到UIImages数组中？

var imagesArray = [UIImage]()
let links = ["http://example.com/image1.jpg","http://example.com/image2.jpg"] as [String]

必须有一个简单的解决方案。 如果它是一个图像，我可以执行以下操作：

let url = URL(string: link2image!)!
let imageData = try? Data(contentsOf: url)
let image = UIImage(data: imageData!)!
self.image.append(image)

Answer 1

最简单的解决方案是遍历数组并使用Data(contentsOf:)同步下载图像，但是，由于同步执行，这将非常不足。

let images = links.flatMap{ link->UIImage? in
guard let url = URL(string: link) else {return nil}
guard let imageData = try? Data(contentsOf: url) else {return nil}
return UIImage(data: imageData)
}

更好的解决方案是并行异步下载图像，我使用 PromiseKit 为此编写了一个UIImage扩展：

extension UIImage {
class func downloadedAsync(fromUrl url: URL)->Promise<UIImage> {
return Promise{ fulfill, reject in
URLSession.shared.dataTask(with: url, completionHandler: { data, response, error in
guard let data = data, error == nil else {
reject(error!); return
}
guard let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
reject(NSError(domain: "Wrong HTTP response code when downloading image asynchronously",code: (response as? HTTPURLResponse)?.statusCode ?? 1000));return
}
guard let mimeType = response?.mimeType, mimeType.hasPrefix("image"), let image = UIImage(data: data) else {
reject(NSError(domain: "No image in response", code: 700)); return
}
fulfill(image)
}).resume()
}
}
}

您可以为如下所示的链接数组调用它：

var imageDownloadTasks = links.flatMap{ link in
guard let url = URL(string: link) else {return nil}
return UIImage.downloadedAsync(fromUrl: url)
}

然后执行承诺：

when(fulfilled: imageDownloadTasks).then{ images in
//use the images, images is of type [UIImage]
}

Answer 2

也许你可以尝试 函数式编程 使用：映射闭包...

links.map({
if let imageData = try? Data(contentsOf: URL(string: $0)!) {
UIImage(data: imageData)
}
})

但是你必须知道如果你的链接是错误的，它会崩溃。所以，我建议你做一些防备来防止这些崩溃。喜欢这个。。。

guard let url = URL(string: $0) else { return nil }

Answer 3

for img in links {
if let data = try? Data(contentsOf: URL(string: img)!) {
let image = UIImage(data: data)
imageArray.append(image!)
}
}