PHPickerViewController 得到 PHAsset

PHPickerViewController 有很多好处，不需要照片权限，体验和系统相册一致，比如支持搜索，性能更好，是独立的进程处理，app想截图都不行，完美的隐私保护。但是也有很多不便，很好用的PHAsset就用不到了。导致不能得到视频地址，需要把视频拷贝到app中。发现 PHPickerResult 有个 assetIdentifier 字段，像能转化为PHAsset，苹果提供了一段代码，如下：

import UIKit
import PhotosUI

class PhotoKitPickerViewController: UIViewController, PHPickerViewControllerDelegate {
    @IBAction func presentPicker(_ sender: Any) {
        let photoLibrary = PHPhotoLibrary.shared()
        let configuration = PHPickerConfiguration(photoLibrary: photoLibrary)
        let picker = PHPickerViewController(configuration: configuration)
        picker.delegate = self
        present(picker, animated: true)
    }
    
    func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {
        picker.dismiss(animated: true)
        
        let identifiers = results.compactMap(\.assetIdentifier)
        let fetchResult = PHAsset.fetchAssets(withLocalIdentifiers: identifiers, options: nil)
        
        // TODO: Do something with the fetch result if you have Photos Library access
    }
}

这段代码得到 assetIdentifier，然后得到 PHAsset，这样就能愉快的玩耍了吗，那是不可能的，有两个坑

• 一是创建PHPickerViewController的时候配置需要传PHPhotoLibrary，要不然会得不到assetIdentifier
• 二是拿到了assetIdentifier，还是拿不到PHAsset，因为还需要照片库的权限。