swift3、PHFetchResult.enumerateObjects错误

Question

在swift 3中，方法是告诉我"ambiguous use of 'enumerateObjects'"，我可以做什么happen.how？

extension PHFetchResult {
public func assetCollection() -> [PHAssetCollection] {
    var list :[PHAssetCollection] = []
    self.enumerateObjects { (object, index, stop) in
        if object is PHAssetCollection {
            let collection = object as! PHAssetCollection
            list.append(collection)
        }
    }
    return list
}
}

Answer 1

做这样的事情能。您不能直接为 PHFetchResult 添加扩展名，因为它有其他 ObjectType 作为其通用参数 PHFetchResult<ObjectType> 。所以你必须做点别的。

class FetchPhoto {

    class func assetCollection() -> [PHAssetCollection] {
        var list :[PHAssetCollection] = []

        PHAssetCollection.fetchMoments(with: nil).enumerateObjects(EnumerationOptions.concurrent) { (collection, _, _) in
                list.append(collection)
        }

        return list
    }
}

PHAssetCollection.fetchMomentsreturnsPHFetchResult<PHAssetCollection>这里PHAssetCollection是ObjectType对PHFetchResult。您收到了不明确的错误，因为您没有指定 objectType。

解决此问题的通用方法。

 class FetchPhoto {

    class func assetCollection<T : PHObject>(result : PHFetchResult<T>) -> [T] {

        var list : [T] = []

        result.enumerateObjects(EnumerationOptions.concurrent) { (object, _, _) in
            list.append(object)
        }

        return list
    }
}

Swift 3

    class PhotosHelper {

        class func fetchAllLocalIdentifiersOfPhotos(completion : (_ localIdentifiers : [String]) -> ()) {

            let photos : PHFetchResult<PHAsset> = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: nil)
            photos.enumerateObjects ({ _,_,_ in

// Do your operations, you can see that there is no warnings/errors in this one
            })

        }
    }

Answer 2

Swift 3.0：只需在 enumerateObjects 之后的花括号开始之前添加 圆括号。

extension PHFetchResult {
  public func assetCollection() -> [PHAssetCollection] {
    var list :[PHAssetCollection] = []
    self.enumerateObjects ({ (object, index, stop) in
        if object is PHAssetCollection {
            let collection = object as! PHAssetCollection
            list.append(collection)
        }
    })
    return list
  }
}

swift3、PHFetchResult.enumerateObjects错误

swift 3, PHFetchResult.enumerateObjects error

swift3