resolver-depends.ts

@ObjectType()
export default class GraphTimeseries {
    @Field()
    assetId: number;
  
    @Field()
    asset: GraphAsset;
  
    @Field(() => [Number])
    eventsOwnerIds: number[] = [];
}

@Resolver(() => GraphTimeseries)
export default class GraphTimeseriesResolver implements ResolverInterface<GraphTimeseries> {
    
    @Query(() => [GraphTimeseries])
    async getTimeseriesByIds(@Arg('ids', () => [Float]) ids: number[], @Ctx() source: Source) {
        return source.getTimeseriesByIds(ids);
    }

    @FieldResolver()
    async asset(@Root() timeseries: GraphTimeseries, @Ctx() source: Source) {
        return await source.getAssetById(timeseries.assetId);
    }
    
    @FieldResolver()
    @DependsOn('asset')
    async eventsOwnerIds(@Root() timeseries: GraphTimeseries, @Ctx() source: Source, @Info() info) {
        const { asset } = timeseries; // No longer undefined.
    }
}