Unions & Interfaces

Introduction

In the Penneo KYC API we use unions and interfaces in several places.
We do this to represent multiple datatypes without having separate queries for each one.

One such example is Screenings which can be found on the Person type

Example

query getPersonWithScreenings($id: ID!) {
    person(id: $id) {
        id
        name

        screeningResults {
            ... on DowJonesScreeningResult {
                source
                matchScore

                names
                title
            
                timeCreated
                timeLastEdited
            }

            ... on DanishPEPListScreeningResult {
                source
                matchScore
                isCurrentlyPEP

                names
            
                timeCreated
                timeLastEdited
            }

            ... on EUSanctionsListScreeningResult {
                source
                matchScore

                names
                birthDates
            
                timeCreated
                timeLastEdited
            }
        }

        timeCreated
        timeLastEdited
    }
}

variables {
    id: <ID>,
}

The screenings field can return either a DowJonesScreeningResult, DanishPEPListScreeningResult or a EUSanctionsListScreeningResult.

They have unique fields and in order to specify which ones for each type, you use the three dots:

... on DanishPEPListScreeningResult

as shown in the example above.

External guide

The Apollo GraphQL project documentation has a good article explaining unions and interfaces in-depth here