Swift:监听 url 属性然后下载照片

Question

我在 viewDidLoad 中运行此代码，但 Profile.currentProfile 还没有 photoUrl，因此它为零，并且此代码永远不会运行

private func getProfilePicture() {
    if let photoURLString = Profile.currentProfile?.photoUrl {
        if let photoURL = URL(string: photoURLString) {
            if let photoData = try? Data(contentsOf: photoURL) {
                self.profilePhotoView.image = UIImage(data: photoData)
                self.letsGoButton.isEnabled = true
            }
        }
    } else {
        self.profilePhotoView.image = UIImage(named: "default-profile-icon")
    }
}

如何等到 photoUrl 不为零，然后运行此代码？谢谢

里克

(编辑)这就是配置文件的设置方式。这在 viewController 实例化之前调用。

func copyProfileFieldsFromFB(completionHandler: @escaping ((Error?) -> Void)) {
    guard AccessToken.current != nil else { return }
    let request = GraphRequest(graphPath: "me",
                               parameters: ["fields": "email,first_name,last_name,gender, picture.width(480).height(480)"])
    request.start(completionHandler: { (_, result, error) in
        if let data = result as? [String: Any] {
            if let firstName = data["first_name"] {
                Profile.currentProfile?.firstName = firstName as? String
            }
            if let lastName = data["last_name"] {
                Profile.currentProfile?.lastName = lastName as? String
            }
            if let email = data["email"] {
                Profile.currentProfile?.email = email as? String
            }
            if let picture = data["picture"] as? [String: Any] {
                if let imageData = picture["data"] as? [String: Any] {
                    if let url = imageData["url"] as? String {
                        Profile.currentProfile?.photoUrl = url
                    }
                }

            }
        }
        completionHandler(error)
    })
}

Answer 1

通常，您需要使用完成处理程序来跟踪异步事件。所以在你的 viewDidLoad() 中你可以调用类似的东西

    Profile.currentProfile?.getPhotoURL { urlString in
        if let photoURL = URL(string: photoURLString) {
        if let photoData = try? Data(contentsOf: photoURL) {
            self.profilePhotoView.image = UIImage(data: photoData)
            self.letsGoButton.isEnabled = true
             }
         }
     }

在你的 Profile 类上，它看起来像这样:

 func getPhotoURL(completion: @escaping (urlString) -> Void) {
     // get urlString
     completion(urlString)
 }