SWIFT ALAssetsLibrary未枚举组

Question

我试图将所有用户图像的缩略图收集到一个数组中，但是当我调用ALAssetsLibrary的enumerateAssetsUsingBlock方法时，似乎什么都没有发生。

import UIKit
import AssetsLibrary

class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate  {


@IBOutlet var photoLibView: UICollectionView
var assetLibrary : ALAssetsLibrary = ALAssetsLibrary()


func showCustomLibrary() {
    self.assetLibrary = ALAssetsLibrary()

    var assetsArray : [ALAsset] = []
    var imageArray : [CGImage] = []
    var count = 0
    var countOne = 0
    let assetsType : ALAssetsGroupType = Int(ALAssetsGroupAll)

    var groupBlock : ALAssetsLibraryGroupsEnumerationResultsBlock = {

        (group: ALAssetsGroup!, stop: UnsafePointer<ObjCBool>) in
        println("is goin")
        count++
        var assetBlock : ALAssetsGroupEnumerationResultsBlock = {
            (result: ALAsset!, index: Int, stop: UnsafePointer<ObjCBool>) in
            imageArray.append(result.thumbnail().takeRetainedValue())
            assetsArray.append(result)
            countOne++
        }

        group.enumerateAssetsUsingBlock(assetBlock)


    }
    var groupFailureBlock : ALAssetsLibraryAccessFailureBlock = {
        (NSError) in
        println("errorrrrrrrr")

    }
    assetLibrary.enumerateGroupsWithTypes(assetsType, usingBlock: groupBlock, failureBlock: groupFailureBlock)



    println("number of groups")
    println(count)
    println("number of total assets")
    println(countOne)

    self.photoLibView.insertItemsAtIndexPaths(imageArray)


}


}

当我运行showCustomLibrary()被调用时，编译器输出number of groups 0 number of total assets 0 fatal error: unexpectedly found nil while unwrapping an Optional value，因为似乎ALAssetsLibrary的组没有被枚举。(没有打印“is goin”)。知道这是怎么回事吗？提前感谢！

Answer 1

我找到问题了。在这个“组”中，结果不应该为零，否则它会迅速崩溃。所以我们应该检查nil case，比如

var groupBlock : ALAssetsLibraryGroupsEnumerationResultsBlock = {

    (group: ALAssetsGroup!, stop: UnsafePointer<ObjCBool>) in
    println("is goin")
    if group != nil
    {
        count++
         var assetBlock : ALAssetsGroupEnumerationResultsBlock = {
            (result: ALAsset!, index: Int, stop: UnsafePointer<ObjCBool>) in
            if result != nil
            {
             imageArray.append(result.thumbnail().takeRetainedValue())
             assetsArray.append(result)
             countOne++
            }
        }
    }

    group.enumerateAssetsUsingBlock(assetBlock)


}

Answer 2

我遇到了存根代码返回节的数量为0的问题，因此我将其更改为1，至少对于我正在处理的示例：https://github.com/thegreatmichael/Albums-iOS8-Swift/blob/master/Albums/IAAlbumsViewController.swift#L66