enumerateGroupsWithTypes loop isn't stopping

Question

I'm using the following code to iterate through eh albums and if it finds the one I need, it should stop further looping.

public func importPhotosFromGallery(albumName: String = "Last Imported") {
    fetchAlbum(albumName) { album, error in
        if let error = error {
            print("Error occurred fetching album: \(error.localizedDescription)")
        } else {
            if let album = album {
                print("found it! \(album.name)")
            }
        }
    }
}

private func fetchAlbum(albumName: String, completion: (album: ALAssetsGroup?, error: NSError?) -> ()) {
    assetsLibrary.enumerateGroupsWithTypes(ALAssetsGroupAlbum, usingBlock: { group, stop in
        if group != nil {
            group.setAssetsFilter(ALAssetsFilter.allPhotos())
            print("group name: \(group.name)")
            if group.name == albumName {
                stop.initialize(true)
                completion(album: group, error: nil)
            }
        } else {
            let notFoundError = NSError.createError("Album Not Found")
            completion(album: nil, error: notFoundError)
        }
    }) { error in
        completion(album: nil, error: error)
    }
}

I'm changing the stop variable's value to true after finding the match but it still executes the else block that returns the notFoundError at the end. This is the output of the print statements.

group name: Last Imported

found it! Last Imported

Error occurred fetching album: Album Not Found

How do I stop this from happening?

Answer 1

The docs for enumerationBlock state

The block to invoke using each asset group in turn.

When the enumeration is done, enumerationBlock is invoked with group set to nil.

That would mean after setting stop to true the enumerationBlock is invoked once more, this time with group being nil and therefore causing the completion(album: nil, error: notFoundError)-branch to be entered.

That results in your completion block getting called twice, once with the correctly found album and once again at the end of the enumeration.

Try inserting a few print-statements to see when which branch is entered and what the input is. In particular wether or not the stop is already set to true.