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
        timeCreated
        timeLastEdited

        screeningResults {
            ... on DowJonesScreeningResult {
                source
                matchScore

                names
                title
            
                timeCreated
                timeLastEdited
            }

            ... on DanishPEPListScreeningResult {
                source
                matchScore
                
                names
                isCurrentlyPEP
                position
            
                timeCreated
                timeLastEdited
            }

            ... on EUSanctionsListScreeningResult {
                source
                matchScore
                
                names
                position
            
                timeCreated
                timeLastEdited
            }
        }
    }
}

variables {
    id: <ID>,
}

The screenings field can return:

• DowJonesScreeningResult,
• DanishPEPListScreeningResult
• EUSanctionsListScreeningResult

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

This enables the client to use one single query to get all screening results on a person, but still have specific data for the specific types.

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