arrays - 从数组中删除重复的 PHAssets？

Question

我正在使用名为 BSImagePicker 的第三方库从照片库中选择多张图像。我可以设置要选择的最大 PHAssets，但是当我显示 BSImagePickerController 以选择更多照片时，问题就来了。这些 PHAssets 只是另外添加到 selectedAssets 并且实际上复制了图像。我尝试删除重复的 PHAsset 和使用的图像，但它不起作用:

extension Array where Element: Equatable {
mutating func removeDuplicates() {
    var result = [Element]()
    for value in self {
        if !result.contains(value) {
            result.append(value)
        }
    }
    self = result
   }
}

func presentBSImagePickerController(vc: BSImagePickerViewController) {
        self.bs_presentImagePickerController(vc, animated: true,
                                             select: { (asset: PHAsset) -> Void in

        }, deselect: { (asset: PHAsset) -> Void in
            // User deselected an assets.

        }, cancel: { (assets: [PHAsset]) -> Void in
            // User cancelled. And this where the assets currently selected.

        }, finish: { (assets: [PHAsset]) -> Void in


            // User finished with these assets

            for i in 0..<assets.count  {
                self.selectedAssets.append(assets[i])
            }
            self.selectedAssets.removeDuplicates()

            self.convertAssetToImages()

        }, completion: nil)
    }

    func convertAssetToImages() -> Void {

        if selectedAssets.count != 0 {

            for i in 0..<selectedAssets.count {

                let manager = PHImageManager.default()
                let option = PHImageRequestOptions()
                var thumbnail = UIImage()
                option.isSynchronous = true

                manager.requestImage(for: selectedAssets[i], targetSize: CGSize(width: 200, height: 200), contentMode: .aspectFill, options: option, resultHandler: {(result, info)->Void in
                    thumbnail = result!

                })

                let data = UIImageJPEGRepresentation(thumbnail, 0.7)
                let newImage = UIImage(data: data!)

                self.photosArray.append(newImage! as UIImage)
                self.photosArray.removeDuplicates()
                print(self.photosArray.removeDuplicates())

                DispatchQueue.main.async {
                    self.collectionView.reloadData() // reloads the collection view on main thread
                }
            }
        }
    }

Answer 1

问题

for i in 0..<assets.count  {
    self.selectedAssets.append(assets[i])
}
self.selectedAssets.removeDuplicates()

...是您的removeDuplicates(除了慢得无法忍受!)只是假设 PHAsset 相等性是重复图像的标记。它不是。 Assets 只是图书馆中内容的临时代表。您想要知道的是 Assets 的本地标识符是否与您已有的 Assets 匹配。我建议这样做:

var ids = Set(self.selectedAssets.map {$0.localIdentifier})
for asset in assets  {
    if !ids.contains(asset.localIdentifier) {
        ids.insert(asset.localIdentifier)
        self.selectedAssets.append(asset)
    }
}

我们列出了我们已有 Assets 的所有本地标识符。然后，仅当其标识符不在列表中时，我们才附加 Assets (及其标识符)。这将多快(因为 Set contains 比 Array contains 快得多)，并且还应该防止“同一张照片”出现两次.