GetNextPage on Playlists from search results deserializes incorrectly

[ellkay-joshe]

Calling GetNextPage on the Playlists from a SearchItemsAsync call doesn't seem to deserialize correctly.

Really simple code sample to reproduce issue:

        var firstPage = await _spotify.SearchItemsAsync("punk", SearchType.Playlist, 50);

        var secondPage = await _spotify.GetNextPageAsync(firstPage.Playlists);

        if (secondPage.Items == null)
        {
            throw new NullReferenceException("Items null");
        }

secondPage.Items ends up being null. Looking at the json it's trying to deserialize, it's because the SimplePlaylist model doesn't match what spotify is returning.

{ "playlists" : { "href" : "https://api.spotify.com/v1/search?query=punk&offset=50&limit=50&type=playlist", "items" : [ { "collaborative" : false, "external_urls" : { "spotify" : "http://open.spotify.com/user/billludwig/playlist/0uxgkOIkRVXe2Y8SRto7YM" ...

Am I doing something wrong? Or does the method need to be updated to handle this? I'd be happy to take a crack at fixing it as long as I'm understanding this correctly. Am I just calling the wrong method?

[JohnnyCrazy]

Ahhh yes, forgot that we also got embedded Paging-objects. (Same for FullPlaylist e.g). The current GetNextPage-method only works for models which are paging objects itself, like Paging<PlaylistTrack> GetPlaylistTracks.

Currently, I've no idea how to solve this. We may need a method in the actual model or something like that. @whereismyspaceship

[ellkay-joshe]

For my own project, I just tried out solving it by deserializing the first nested member for GetNextPage instead of the root -- looks like the playlists member on the json result matches up with SimplePlaylist, so if i just grab it and deserialize THAT to Paging, I feel like it should work? Unless I'm wrong and the models don't line up.

Other issue I'm seeing is the API is returning null for bool & int values for this search (Collaborative, Public, Images.Height, etc). Not sure what to do there -- is there a way to get Newtonsoft to just make those deserialize as default(T)? Should those members maybe be nullables?

[ellkay-joshe]

For my own project, I just tried out solving it by deserializing the first nested member for GetNextPage instead of the root -- looks like the playlists member on the json result matches up with SimplePlaylist, so if i just grab it and deserialize THAT to Paging, I feel like it should work? Unless I'm wrong and the models don't line up.

Other issue I'm seeing is the API is returning null for bool & int values for this search (Collaborative, Public, Images.Height, etc). Not sure what to do there -- is there a way to get Newtonsoft to just make those deserialize as default(T)? Should those members maybe be nullables?

<edit> whoops, that was just an error in my implementation. Wasn't using the json serializer settings.

[JohnnyCrazy]

Mh, I think I just found a well-working solution @one-eyed-man :

//Set return type specifically:
SearchItem item = _spotify.SearchItems("punk", SearchType.Playlist);
var next1 = _spotify.GetNextPage<SearchItem, SimplePlaylist>(item.Playlists);

//But also keep Old Behavior:
Paging<PlaylistTrack> tracks = _spotify.GetPlaylistTracks("artk0ree", "3POl19QMYMtxddwvLe3NZB");
var next2 = _spotify.GetNextPage(tracks);

Implementation:

public V GetNextPage<V, T>(Paging<T> paging)
{
    if (!paging.HasNextPage())
        throw new InvalidOperationException("This Paging-Object has no Next-Page");
    return DownloadData<V>(paging.Next);
}
public Paging<T> GetNextPage<T>(Paging<T> paging)
{
    return GetNextPage<Paging<T>, T>(paging);
}

Will implement and release tomorrow 😉

[JohnnyCrazy]

Fixed and implemented in 8bde064

Usage:

Paging<PlaylistTrack> tracks = _spotify.GetPlaylistTracks("artk0ree", "3POl19QMYMtxddwvLe3NZB");
Paging<PlaylistTrack> tracks2 = _spotify.GetNextPage(tracks);

SearchItem search = _spotify.SearchItems("punk", SearchType.Playlist);
SearchItem search2 = _spotify.GetNextPage<SearchItem, SimplePlaylist>(search.Playlists);