In GraphQL, how can I specify nested arrays as a field type? - graphql-js

Question

In GraphQL, I'm trying to create a GeoJSON object type.
When I specify a 4-dimensional array of GraphQLFloats, I get an error when I start my server:
Error: Decorated type deeper than introspection query.
The type definition looks like this:
var GraphQLGeoJSON = new GraphQLObjectType({
name: 'GeoJSON',
fields: {
type: {
type: GraphQLString,
resolve: (obj) => obj.type,
},
coordinates: {
type: new GraphQLList(new GraphQLList(new GraphQLList(new GraphQLList(GraphQLFloat)))),
resolve: (obj) => obj.coordinates,
}
}
});
How can I resolve this error? This is where it's thrown in the source:
https://github.com/graphql/graphql-js/blob/568dc52a4f9cc9bdec4f9283e6e528970af06cde/src/utilities/buildClientSchema.js#L105

Answer 1

We ended up defining a GeoJSON scalar type instead of an object type. This would allow us to perform strict validations against the GeoJSON spec. For now, just to keep us moving, we've defined a (completely unimplemented) custom GeoJSON type:
var GeoJSON = new GraphQLScalarType({
name: 'GeoJSON',
serialize: (value) => {
// console.log('serialize value', value);
return value;
},
parseValue: (value) => {
// console.log('parseValue value', value);
return value;
},
parseLiteral: (ast) => {
// console.log('parseLiteral ast', ast);
return ast.value;
}
});
... which allows us to use it like this:
var Geometry = new GraphQLObjectType({
name: 'Geometry',
fields: () => ({
id: globalIdField('Geometry'),
geojson: {
type: GeoJSON,
},
},
};
You could use this strategy to define a custom type to represent an array of arrays, or define a custom type to represent just the nested arrays, and then use new GraphQLList(CoordinatesType), etc. It depends on the data you're modeling.