Apolloclient with more than 2 ApolloLinks

Question

We have defined an ApolloClient with two ApolloLinks, connecting with MongoDB and PostgreSQL and it is working perfectly:

const firstLink = new HttpLink({
  uri: 'graphql-postgre',
  //headers: yourHeadersHere,
  // other link options...
});
const secondLink = new HttpLink({
  uri: 'graphql-mongodb',
  //headers: yourHeadersHere
  // other link options...
});


const client = new ApolloClient({
 link: ApolloLink.split(
 o => o.getContext().clientName === "mongo", 
 secondLink, 
 firstLink // by default -> postgre)
 ),
 cache: new InMemoryCache(),
 fecthOptions: {
 mode: 'no-cors'
 },
 shouldBatch: true
});

Now, we need to add a new link in order to have access to a new database (Neo4J), but we can't find any example and we don't know if it is possible to use more than two sources. We have tried the following code, trying to include some logic in the second link but it doesn't work as we expected. We get information from the first and the second link but not from the third one:

const thirdLink = new HttpLink({
  uri: 'graphql-neo4j',
  //headers: yourHeadersHere
  // other link options...
});

const client = new ApolloClient({
  link: ApolloLink.split(
    o => o.getContext().clientName === "mongo", 
    secondLink, 
      (o => o.getContext().clientName === "neo", 
      thirdLink,
      firstLink) // by default -> postgre)
  ),
  cache: new InMemoryCache(),
  fecthOptions: {
    mode: 'no-cors'
  },
  shouldBatch: true
});

Thank you in advance.

Answer 1

unfortunately ApolloLink.split allows only 2 options, but you can still bypass that limitation using this approach

const client = new ApolloClient({
link: ApolloLink.split(
(o) => o.getContext().clientName === 'mongo',
secondLink,
ApolloLink.split((o) => o.getContext().clientName === 'neo',
  thirdLink,
  firstLink)
), // by default -> postgre)
cache: new InMemoryCache(),
fecthOptions: {
mode: 'no-cors',
},
shouldBatch: true,
});