视频 URL pathExtension 找不到 nil

Question

我正在获取数组中的所有图像和视频作为 PHAsset，然后尝试获取它们的 URL。在代码的下一部分中，我试图获得 URL 路径扩展，但在这一行中我遇到了错误。我的代码如下：

var imagesAndVideos: PHFetchResult<PHAsset>!
let asset = imagesAndVideos!.object(at: indexPath.row)

func grabPhotos(){
let imgManager = PHImageManager.default()


let fetchOptions = PHFetchOptions()
fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]


fetchOptions.predicate = NSPredicate(format: "mediaType == %d || mediaType == %d",
                                         PHAssetMediaType.image.rawValue,
                                         PHAssetMediaType.video.rawValue)

imagesAndVideos = PHAsset.fetchAssets(with: fetchOptions)
}

var ext:String!
var url:NSURL!

imgManager.requestAVAsset(forVideo: asset, options: nil, resultHandler: {(asset: AVAsset?, audioMix: AVAudioMix?, info: [AnyHashable : Any]?) in

            DispatchQueue.main.async(execute: {
            let myAsset = asset as! AVURLAsset

            url = myAsset.url as NSURL
            self.photoLibraryVideoUrl.append(url)
            let videoData = NSData(contentsOf : url as URL)
            self.videoDataArray.append(videoData!)
            })

        })

   ext = "."+url.pathExtension!
   self.nameArray.append(dateStringForFolder+ext)

这行显示 url 为 nil:

ext = "."+url.pathExtension!

这个错误不是每次都显示。我认为 (ext = "."+url.pathExtension!) 代码在 url 获得价值之前执行。我怎么解决这个问题？

Answer 1

requestAVAsset 是一个异步函数，一旦执行完成就会调用闭包。所以 ext = "."+url.pathExtension! 和 self.nameArray.append(dateStringForFolder+ext) 甚至可以在 requestAVAsset 完成闭包执行之前执行。您必须将代码移动到闭包内。

imgManager.requestAVAsset(forVideo: asset, options: nil, resultHandler: {(asset: AVAsset?, audioMix: AVAudioMix?, info: [AnyHashable : Any]?) in
    DispatchQueue.main.async(execute: {
        let myAsset = asset as! AVURLAsset
        url = myAsset.url as NSURL
        self.photoLibraryVideoUrl.append(url)
        let videoData = NSData(contentsOf : url as URL)
        self.videoDataArray.append(videoData!)
        ext = "."+url.pathExtension!
        self.nameArray.append(dateStringForFolder+ext)
    })

})

视频 URL pathExtension 找不到 nil

Video URL pathExtension find nil

ios

swift3