swift 3, PHFetchResult.enumerateObjects error - swift3

Question

In swift 3,the method is show me "ambiguous use of 'enumerateObjects'",what happen.how can i do?
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

Swift 3.0: Just add the Round Brackets before Curly Brackets starts after enumerateObjects.
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 2

Do something like this noh. You can't directly add extension for PHFetchResult because it has other ObjectType as its generic parameter PHFetchResult<ObjectType> . So you must do something else.
class FetchPhoto {
class func assetCollection() -> [PHAssetCollection] {
var list :[PHAssetCollection] = []
PHAssetCollection.fetchMoments(with: nil).enumerateObjects(EnumerationOptions.concurrent) { (collection, _, _) in
list.append(collection)
}
return list
}
}
PHAssetCollection.fetchMoments returns PHFetchResult<PHAssetCollection> here PHAssetCollection is the ObjectType for the PHFetchResult. You got the ambiguous error because you have not specified the objectType.
A generic way to approach this.
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
})
}
}