Understanding GraphQL Interfaces

Understanding GraphQL Interfaces

An interface in GraphQL acts as a blueprint for a collection of fields and types, that can be reused by some other field or types in a GraphQL query. With its help, we can define some common set of interfaces, and use those in our actual schema to abstract out our business logic, and give our schema greater flexibility....

Defining Interfaces in GraphQL Schema

We define an interface with the help of the “interface” keyword in a GraphQL Schema, followed by an interface name, and the fields that we want to list out and be represented by it....

Querying Interface Fields

We will look at how we can query interface fields directly from a GraphQL API, and how the server will return the appropriate fields based on the type of the queried object....

Implementing Interfaces in Mutations

We can implement interfaces in the mutations itself where the mutations require an input object to be passed in its argument. With the interface as its type, the input object will be expected to have the same types as its interface....

Handling Interfaces in Resolvers

Interfaces can be used inside the GraphQL resolvers as well to resolve their fields dynamically based on a specific condition or the concrete type of the return object. Let’s look at a simplified example below –...

Conclusion

In this article, we learnt about interfaces in GraphQL Schema, and how we can use it to create a common definition of certain fields that can we reused by other fields in a GraphQL query. We also looked at some examples, and saw how we can use interfaces in a GraphQL query. Interfaces help enhance flexibility of the schema, and allow reuse of common fields that are frequently used in other places....