Unions

Defining Union Types
Union types are defined with a list of object types:
const builder = new SchemaBuilder<{
    Objects: {
        GiraffeStringFact: { factKind: 'string'; fact: string };
        GiraffeNumericFact: { factKind: 'number'; fact: string; value: number };
    };
}>({});
​
builder.objectType('GiraffeStringFact', {
    fields: (t) => ({
        fact: t.exposeString('fact', {}),
    }),
});
​
const GiraffeNumericFact = builder.objectType('GiraffeNumericFact', {
    fields: (t) => ({
        fact: t.exposeString('fact', {}),
        value: t.exposeFloat('value', {}),
    }),
});
​
const GiraffeFact = builder.unionType('GiraffeFact', {
    types: ['GiraffeStringFact', GiraffeNumericFact],
    resolveType: (fact) => {
        switch (fact.factKind) {
            case 'number':
                return GiraffeNumericFact;
            case 'string':
                return 'GiraffeStringFact';
        }
    },
});
The types array can either contain Object type names defined in TypeInfo, or and Object Ref created by object type. builder.objectType, builder.objectRef or other method, or a class that was used to implement an object type.
The resolveType function will be called with each item returned by a field that returns the unionType, and is used to determine which concrete the value corresponds to. It is usually good to have a shared property you can use to differentiate your union members.
Using Union Types
builder.queryField('giraffeFacts', (t) =>
    t.field({
        type: [GiraffeFact],
        resolve: () => {
            const fact1 = {
                factKind: 'string',
                fact:
                    'A giraffe’s spots are much like human fingerprints. No two individual giraffes have exactly the same pattern',
            } as const;
​
            const fact2 = {
                factKind: 'number',
                fact: 'Top speed (MPH)',
                value: 35,
            } as const;
​
            return [fact1, fact2];
        },
    }),
);
Interfaces
Printing Schema
Last updated 3 months ago