#GRAPHQL FRAGMENTS HOW TO#

Let’s attach a resolver to the arch field. Union SearchResult = Conference | Festival | Concert | Venue You can follow along by navigating to the console andĪdding the following under the Schema page: _typename is required for return types that are interfaces or unions. import gql from graphql-tag const userFragment gql fragment Useruser on User. _typename, whose value corresponds to the identified object type name. A JavaScript template literal tag that parses GraphQL queries. With AWS AppSync, this hint is represented by a meta field named Must be given a hint to identify our possible types from the raw results. SearchResult union defined (that is, Conference,īecause the logic to identify a Festival from a Venue or aĬonference is dependent on the application requirements, the GraphQL engine

The results list must present itself as one of the possible types that the Type resolution is the mechanism by which the GraphQL engine identifies a resolved valueĬoming back to the union search example, provided our query yielded results, each item in Using theĮvent schema, you can define a SearchResult union as Preferred over interfaces when the possible types do not share a logical hierarchy.įor example, a search result might represent many different types. Interfaces, except that they don’t define a common set of fields. The GraphQL type system also supports Unions. From there we make a regular GraphQL call for the HeroBlock. Here, we have an example using the HeroBlock: We start off by declaring this as a fragment called HeroBlock. Represent common characteristics is very helpful for sorting The way we build the fragments is exactly how we implement parts of the original GraphQL call. Since results are returned as a single collection of events, using interfaces to Let’s examine an example of a GraphQL query that uses the interface. You can access the fields on any implementing type using GraphQL fragments, as long as you specify Because GraphQL interfaceįields are common to all the implementing types, it’s possible to select any fields on theĮndsAt, venue, and minAgeRestriction). In Schema Definition Language (SDL), the Event interface is defined as follows:įindEventsByVenue returns a list of Event. Speakers and workshops, while a Concert features a performing band.

These types also have differences, a Conference offers a list of These types all share commonĬharacteristics, including a name, a venue where the event is taking place, and a start andĮnd date. Possible kinds of events are Concert,Ĭonference, and Festival.

#GRAPHQL FRAGMENTS HOW TO#

To simplify getting started with GraphQL, learn how to automatically create andįor example, we could represent an Event interface that represents any kind

If you are just getting started with GraphQL, you should return to this topic at a later time when you want to evolve your schema or add more features. An interface exposes a certain set of fields that a type must include The GraphQL type system supports Interfaces. gql files, see Webpack loading and preprocessing below.This topic provides an overview of interface and union types in GraphQL. It also means you can use = to compare queries to check if they are identical. This means that if you call the tag on the same query multiple times, it doesn't waste time parsing it again. This package only has one feature - it caches previous parse results in a simple dictionary. That's where this package comes in - it lets you write your queries with ES2015 template literals and compile them into an AST with the gql tag. However, strings are inconvenient to manipulate, if you are trying to do things like add extra fields, merge multiple queries together, or other interesting stuff. GraphQL strings are the right way to write queries in your code, because they can be statically analyzed using tools like eslint-plugin-graphql. User_user fragment in the graphQL selection set, this requirement makes static analysis by tools such as eslint-plugin-graphql possible. Hit the arrow button next to the StepZen logo, and you'll get your results back Now, since we're requesting all fields on both queries, we have an opportunity to use Fragments Normally, you'd have to go back into. A GraphQL Fragment is a reusable unit of a GraphQL query, which creates a shared piece of query logic. Click 'Explorer' -> select 'BreedById' and 'allBreeds' and select all the available fields. You can think of it as functions in programming languages, that are reusable units. Note: While it may seem redundant to have to both embed the userFragment variable in the template literal AND spread the. A GraphQL fragment lets you build multiple fields, and include them in multiple queries.

Graphql fragments