Discussion on: A Beginner’s Guide to GraphQL

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In the example to return a single user:

query {    
    user(id: 1) {    
        id    
        name    
        email    
        age    
    }    
}

I get the error:

{
  "errors": [
    {
      "message": "Cannot return null for non-nullable field Query.user.",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "user"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "Error: Cannot return null for non-nullable field Query.user.",
            "    at completeValue (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:631:13)",
            "    at completeValueWithLocatedError (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:580:21)",
            "    at completeValueCatchingError (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:550:12)",
            "    at resolveField (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:497:10)",
            "    at /Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:364:18",
            "    at Array.reduce (<anonymous>)",
            "    at executeFields (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:361:42)",
            "    at executeOperation (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:289:122)",
            "    at executeImpl (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:154:14)",
            "    at Object.execute (/Users/danielbraun/Sites/graphql-server/node_modules/graphql/execution/execute.js:131:35)"
          ]
        }
      }
    }
  ],
  "data": null
}

Leonardo Maldonado • Jan 9 '19 • Edited

I really think that this error came from de db.js, did you uploaded it right? Can you upload this code in someplace? I may be able to help you if you do so.

Maarten Dings • Jan 9 '19

That's the type checking (===) failing there. I had the same issue. Replace the find functions to double equal checks instead of triple, then it should work: users.find(user => user.id == id)
Not sure why the typecheck doesn't work. Perhaps the ID! in schema.graphql is returning a string by default?