Setting Up Union Type With Multiple Entities

[cameronmakarchuk]

Hi, just wondering the best approach for this as I'm running into a "property not found" error with my setup.

I have 3 subgraphs (Products, Content, Listing). In Content I have a union type that includes 2 entities (ProductPayload and ListingPayload):

UnionType = Builder.unionType('UnionType', {
   types: [ProductType, ListingType, AppType],
   resolveType: ({contentType}) => {
       ... if (contentType === 'PRODUCT') {
          return ProductType
      }

      ..... other conditions...
   }
})

In the resolveType() I'm getting an error saying "contentType does not exist on ...." because the keys for ProductPayload and Listing entities don't include contentType.

const SampleReference= builder.objectRef<SampleBackingType>(SampleReference').implement({
	fields: (t) => ({
		id: t.exposeString('id'),
		label: t.exposeString('label', { nullable: true }),
		contentType: t.field({
			type: CONSTANTS.ReferenceContentType,
			resolve: ({ contentType }) => {
				return contentType;
			},
		}),
		content: t.field({
			type: BlockReferenceContent,
			nullable: true,
			resolve: ({ contentType, id, ...additionalFields }, _, __, { variableValues }) => {
				if (!id || !contentType) {
					return null;
				}

				const { language, channel, client } = variableValues;

				let result = null;
				switch (contentType) {
					case CONSTANTS.ReferenceContentTypeEnum.PRODUCT:
						result = {
							id,
							channel,
							language,
							client,
						};
						break;
					case CONSTANTS.ReferenceContentTypeEnum.COLLECTION:
						result = {
							id,
							channel,
							language,
							client,
						};
						break;
					case CONSTANTS.ReferenceContentTypeEnum.APP_URL:
						result = {
							id,
							...additionalFields,
						};
						break;
					default:
						result = null;
						break;
				}

				if (!result) {
					return null;
				}

				return {
					...result,
					contentType,
				};
			},
		}),
	}),
});

I thought adding contentType to the return at the bottom would solve the issue but it didn't.

Any suggestions on where I might have the setup wrong?

[hayes]

There are a number of different options here.

In your resolve type, you can do something like `resolveType: (source) => if ('contentType' in source && source.contentType === 'PRODUCT')

Adding contentType to the returned values in the parent resolver isn't suffient because typescript doesn't know about all the fields that return your union type, it only knows about the types that make up the union type, so you would need to add contentType to all of the individual types that make up the union.

Another option is to remove the need for the resolveType function. You can do this by adding __typename to the returned values instead. Alternatively, you can use the brandWithType utility function

[cameronmakarchuk]

Thanks so much for the quick reply! That first option solved the issue, but I may play around with the other options too to see which fits best.