使用Relay时本地化GraphQL结果

Question

I'm hoping someone in the GraphQL/Relay community has encountered this issue.

We have a multilingual system, which means that the results are localized. So we have an argument called lang which is passed down to the field resolvers.

Queries are written as such:

query {
  viewer(lang: ja) {
    books { <- Type is `Book`
      id
      title <- This would be localized to Japanese.
    }
  }
}

Which would return:

{
  "data": {
    "viewer": {
      "books": [
        {
          "id": "SOMETHINGSOMETHING123",
          "name": "ハリー・ポッター" // "Harry Potter" in Japanese.
        }
      ]
    }
  }
}

This is possible due to the resolver for translatable fields looking like this (note that I am using dataloader ):

...
resolve: (parent, args, ast, { rootValue }) => {
  const { language } = rootValue
  const { BookLoader } = rootValue.loaders
  return BookLoader.TranslationsLoader(language).load(parent.id).then(translations => translations[parent.id].title || parent.title)
}

If a translation exists, it will use that instead of the original value. This was working fine until we introduced Relay into our project.

We want to utilize Relay's node , and have made it partially work, ie:

query {
  node(id: "SOMETHINGSOMETHING123") {
    ...b
  }
}
fragment b on Book {
  id
  name
}

But since using node can't take arguments like viewer can, there is no way to pass the language.

How would I pass language parameters to the resolver which would work with both standard queries and nodes?

Answer 1

Since graphql-js v0.6 , each resolver receives a context object as the third parameter. This is good for passing contextual info from the server to GraphQL's execution phase. We use it, for example, to handle authentication and authorization. You could pass in the desired language there. If you use express-graphql or koa-graphql , they pass the request object as the context by default. You could examine the headers from the resolver.

EDIT: Here is an example of handling a session in a graphql resolver using express-graphql: express-graphql