public override void OnConfigure(
IDescriptorContext context,
IObjectFieldDescriptor descriptor,
MemberInfo member)
{
descriptor.Resolve(async ctx =>
{
ICharacter character = ctx.Parent <ICharacter>();
ICharacterRepository repository = ctx.Service <ICharacterRepository>();
//This is injected by the PreProcessing middleware wen enabled...
var graphQLParams = new GraphQLParamsContext(ctx);
//********************************************************************************
//Perform some pre-processed retrieval of data from the Repository...
//Notice Pagination processing is pushed down to the Repository layer also!
//Get RepoDb specific mapper for the GraphQL parameter context...
//Note: It's important that we map to the DB Model (not the GraphQL model).
var repoDbParams = new GraphQLRepoDbMapper <CharacterDbModel>(graphQLParams);
//Now we can retrieve the related and paginated data from the Repo...
var pagedFriends = await repository.GetCharacterFriendsAsync(character.Id, repoDbParams.GetCursorPagingParameters());
return(new PreProcessedCursorSlice <ICharacter>(pagedFriends));
//********************************************************************************
});
}
protected override ValueTask <Connection> SliceAsync(IResolverContext context, object source, CursorPagingArguments arguments)
{
//If Appropriate we handle the values here to ensure that no post-processing is done other than
// correctly mapping the results into a GraphQL Connection as Edges with Cursors...
if (source is IPreProcessedCursorSlice <TEntity> pagedResults)
{
bool includeTotalCountEnabled = this.PagingOptions.IncludeTotalCount ?? PagingDefaults.IncludeTotalCount;
var graphQLParamsContext = new GraphQLParamsContext(context);
//Optimized to only require TotalCount value if the query actually requested it!
if (includeTotalCountEnabled && graphQLParamsContext.IsTotalCountRequested && pagedResults.TotalCount == null)
{
throw new InvalidOperationException($"Total Count is requested in the query, but was not provided with the results [{this.GetType().GetTypeName()}] from the resolvers pre-processing logic; TotalCount is null.");
}
int?totalCount = pagedResults.TotalCount;
//Ensure we are null safe and return a valid empty list by default.
IReadOnlyList <IndexEdge <TEntity> > selectedEdges =
pagedResults?.ToEdgeResults().ToList() ?? new List <IndexEdge <TEntity> >();;
IndexEdge <TEntity>?firstEdge = selectedEdges.FirstOrDefault();
IndexEdge <TEntity>?lastEdge = selectedEdges.LastOrDefault();
var connectionPageInfo = new ConnectionPageInfo(
hasNextPage: pagedResults?.HasNextPage ?? false,
hasPreviousPage: pagedResults?.HasPreviousPage ?? false,
startCursor: firstEdge?.Cursor,
endCursor: lastEdge?.Cursor,
totalCount: totalCount ?? 0
);
var graphQLConnection = new Connection <TEntity>(
selectedEdges,
connectionPageInfo,
ct => new ValueTask <int>(connectionPageInfo.TotalCount ?? 0)
);
return(new ValueTask <Connection>(graphQLConnection));
}
throw new GraphQLException($"[{nameof(PreProcessedCursorPagingHandler<TEntity>)}] cannot handle the specified data source of type [{source.GetType().Name}].");
}
public override void OnConfigure(
IDescriptorContext context,
IObjectFieldDescriptor descriptor,
MemberInfo member)
{
descriptor.Resolver(ctx =>
{
ICharacter character = ctx.Parent <ICharacter>();
ICharacterRepository repository = ctx.Service <ICharacterRepository>();
//********************************************************************************
//Perform some pre-processed Paging (FYI, without sorting this may be unprdeicatble
// but works here due to the in-memory store used by Star Wars example!
var graphQLParams = new GraphQLParamsContext(ctx);
var friends = repository.GetCharacters(character.Friends.ToArray());
var pagedFriends = friends.SliceAsCursorPage(graphQLParams.PagingArgs);
return(new PreProcessedCursorSlice <ICharacter>(pagedFriends));
//********************************************************************************
});
}
protected override ValueTask <CollectionSegment> SliceAsync(IResolverContext context, object source, OffsetPagingArguments arguments)
{
//If Appropriate we handle the values here to ensure that no post-processing is done other than
// correctly mapping the results into a GraphQL Collection Segment with appropriate Paging Details...
if (source is IPreProcessedOffsetPageResults <TEntity> pagedResults)
{
bool includeTotalCountEnabled = this.PagingOptions.IncludeTotalCount ?? PagingDefaults.IncludeTotalCount;
var graphQLParamsContext = new GraphQLParamsContext(context);
//Optimized to only require TotalCount value if the query actually requested it!
if (includeTotalCountEnabled && graphQLParamsContext.IsTotalCountRequested && pagedResults.TotalCount == null)
{
throw new InvalidOperationException($"Total Count is requested in the query, but was not provided with the results [{this.GetType().GetTypeName()}] from the resolvers pre-processing logic; TotalCount is null.");
}
int?totalCount = pagedResults.TotalCount;
//Ensure we are null safe and return a valid empty list by default.
var segmentResults = pagedResults?.ToList() ?? new List <TEntity>();
var collectionSegmentInfo = new CollectionSegmentInfo(
hasNextPage: pagedResults?.HasNextPage ?? false,
hasPreviousPage: pagedResults?.HasPreviousPage ?? false
);
var graphQLConnection = new CollectionSegment(
(IReadOnlyCollection <object>)segmentResults,
collectionSegmentInfo,
ct => new ValueTask <int>(totalCount ?? throw new InvalidOperationException())
);
return(new ValueTask <CollectionSegment>(graphQLConnection));
}
throw new GraphQLException($"[{nameof(PreProcessedOffsetPagingHandler<TEntity>)}] cannot handle the specified data source of type [{source.GetType().Name}].");
}
