获取保存到照片库的图像的PHAsset/localIdentifier

Question

我正在使用UIImageWriteToSavedPhotosAlbum将图像保存到照片应用程序中。这是我发现的唯一一个可以让你做到这一点的函数。

这是我的代码：

import UIKit
import Photos
class ViewController: UIViewController {
/// photo of a cactus
let photoURL = URL(string: "https://raw.githubusercontent.com/aheze/DeveloperAssets/master/cactus.png")! /// in my app it's actually a local URL, but this also works

func saveToPhotos() {
DispatchQueue.global().async {
let data = try? Data(contentsOf: self.photoURL)
let image = UIImage(data: data!)
UIImageWriteToSavedPhotosAlbum(image!, self, #selector(self.image(_:didFinishSavingWithError:contextInfo:)), nil)
}
}
/// called when the image saving is complete
@objc func image(_ image: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) {
print("Finished saving image")

/// how to get localIdentifier of the image?
let asset = PHAsset() /// obviously this does not work...
let localIdentifier = asset.localIdentifier
}
}

图像已成功保存到照片应用程序。然而，我需要保留对它的引用，最好是它的localIdentifier，这样我将来就可以在用户的其他照片中找到它。

例如，当我稍后调用fetchAllPhotos时，我需要一些方法来定位我保存的仙人掌照片。

var allPhotos: PHFetchResult<PHAsset>?
func fetchAllPhotos() {
let fetchOptions = PHFetchOptions() /// get all of user's photos
allPhotos = PHAsset.fetchAssets(with: .image, options: fetchOptions)

if let photos = allPhotos {
photos.enumerateObjects { (asset, index, stop) in

/// I need to find the image!  
/// So I need to know its localIdentifier back when I saved it.
if asset.localIdentifier == "cactus" {
print("photo has been found")
}
}
}
}

有什么办法我能做到这一点吗？UIImageWriteToSavedPhotosAlbum完成处理程序引用了UIImage，所以也许我可以从中创建一个PHAsset？或者我可以写一些东西到UIImage的元数据，我不确定。

Answer 1

尝试保存图像逻辑：

try PHPhotoLibrary.shared().performChangesAndWait {
let imgReq = PHAssetChangeRequest.creationRequestForAsset(from: image)
self.localID = imgReq.placeholderForCreatedAsset.localIdentifier
}

您可以按如下方式获取本地ID：

photos.enumerateObjects { (asset, index, stop) in
if asset.localIdentifier == self.localID {
print("photo was found")
}
}