How to access a response header in the FetchResponse (client side)

[shaundclements]

Can anyone advise how I can retrieve a response header in my client (React Code) - I am using the useQuery hook but it seems rather limited.

Ive also tried modifying the response data returned back to the client (see 'Modifying response data' from https://www.apollographql.com/docs/react/networking/advanced-http-networking) with an extra field returned back but it seems to be readonly.

[phryneas]

The problem here is that Apollo Client is a GraphQL client and doesn't really know about HTTP concepts outside of the Link chain - the query could be made any number of different ways, http only being one of them.

Your second attempt (adding it to the response data) could work, but would need quite a lot more work:

• use a document transform to add a new field to the outgoing query (this way the cache is aware of that field and will parse it off the response)
• in the link chain, remove that field for outgoing requests so the server doesn't see it
• in the link chain, add the field value back for incoming responses

[shaundclements]

going to try your suggestion thanks, I am surprised there is no access to the response headers given the client is making an http request

[shaundclements]

@phryneas for your first two points, is that done in the query definition 'SelectionSet' and 'loc' ?
For your last point, is that just response.data area ?

[phryneas]

I am surprised there is no access to the response headers given the client is making an http request

As I said, the Client is agnostic to the transport method you are using, which is why it's not aware of this. You could also e.g. use WebSockets for this - the Client is a pure GraphQL client, not a HTTP Client.

for your first two points, is that done in the query definition 'SelectionSet' and 'loc' ?

Yes! As examples you can see the addTypeNameToDocument transform and the other transforms in the same file.

For your last point, is that just response.data area ?

Yes, your data shape would have to match up with the shape of the query you pass into the link chain.