功能不等待 Swift 中使用 Alamofire 下载图片

Question

我尝试使用 Alamofire 下载图片，此图片必须附加到自定义 class。但我没有那样做。图片是异步下载的，我没有解决这个问题。我的错误在哪里？

图像始终return无

// 标记：自定义函数

import UIKit
import Alamofire
import AlamofireImage

class DownloadPhotoWAlamofire {

func download(imageUid:String , completion : @escaping (UIImage) -> ()  )  {
    let url = "\(Config.fileService)file?uid=\(String(describing: imageUid))"
    print("URL \(url)")

    Alamofire.request(url, method: .get ).responseImage { response in
        print("Image Response \(response)")

        let image = response.result.value
        completion(image!)

        }
    }
}

// 标记：在 VIEWCONTROL 中

guard let objectElement = o as? [String:Any] else {return}
let managerName = objectElement["managerName"] as? String
let managerAvatarUid = objectElement["managerProfilePictureFileUid"] as? String
let assistantsOfDiariesUid = objectElement["assistantsOfDiariesUid"] as? String

var image:UIImage? = nil

if managerAvatarUid != nil {
    DownloadPhotoWAlamofire().download(imageUid: managerAvatarUid!, completion: { (imageD) in
                    image = imageD
                })
     }

 let e = AssistantInviteElement(managerName: managerName!, managerAvatarUid: managerAvatarUid, assistantsOfDiariesUid: assistantsOfDiariesUid!,avatarImage:image)
 self.managerList.append(e)

Answer 1

将其更改为：

if managerAvatarUid != nil {
    DownloadPhotoWAlamofire().download(imageUid: managerAvatarUid!, completion: { (imageD) in
        let image = imageD
        let e = AssistantInviteElement(managerName: managerName!, managerAvatarUid: managerAvatarUid, assistantsOfDiariesUid: assistantsOfDiariesUid!,avatarImage:image)
        self.managerList.append(e)
    })
}

由于下载是异步调用，您在下载图像之前执行了这一行：

let e = AssistantInviteElement(managerName: managerName!, managerAvatarUid: managerAvatarUid, assistantsOfDiariesUid: assistantsOfDiariesUid!,avatarImage:image)

当时图片为零。所以只有当你下载了图像并且它应该可以工作时才调用它。

也不要用“！”展开可选，做一个 if let/guard let。因此，将 Almofire 代码更改为：

Alamofire.request(url, method: .get ).responseImage { response in
    print("Image Response \(response)")
    if let image = response.result.value {
        print("image downloaded: \(image)")
        completion(image)
    } else {
        print("Image is nil")
    }
}

Answer 2

启动异步下载后直接设置图片，当然还是nil。在代码中使用回调的要点是，一旦回调被调用，您就只能使用请求的资源；所以你应该将使用图像的代码移到回调块中。

功能不等待 Swift 中使用 Alamofire 下载图片

Function doesnt wait download Picture with Alamofire in Swift

ios

swift

alamofire

alamofireimage