Why does GraphQL reference crash when embedded in Object vs JSX?

Question

I am currently using GraphQL to query my WordPress server which I'm using as a backend.

Everything is working as it should be so far, this is my graphQL query:

const GET_ALL_MEDIA = gql`
  query MyQuery {
    slumpMedias(first: 100) {
      edges {
        node {
          title
          slumpMeta {
            image {
              mediaItemUrl
            }
            audio1 {
              mediaItemUrl
            }
          }
        }
      }
    }
  }
`;


function Items() {
  const { loading, error, data } = useQuery(GET_ALL_MEDIA);

   return (
     <div>
       <h2>{data.slumpMedias.edges[5].node.title}</h2>
     </div>
    );
}

This renders perfectly, and I can see the correct title rendered in front of me.

Now That I have access to the nodes that I need I would like to start building a new data structure above the JSX. My only issue is that when I start construct this object and make the same reference, my program crashes to an empty screen.

This is the difference in code:

function Items() {

  const { loading, error, data } = useQuery(GET_ALL_MEDIA);
  console.log(data);

  const objects = [
    {
      id: 0,
      title: data.slumpMedias.edges[6].node.title,
      image: "/images/1.png",
      sound: "https://google.com",
      items: [],
    },    
  ];

  

  return <Display objects={objects}></Display>;
}

I notice that the title does update briefly leading me to believe that the reference is correct, it's just that on refresh I'm met with a blank screen.

The error message:

Items.js:35 Uncaught TypeError: Cannot read properties of undefined (reading 'slumpMedias')
    at Items (Items.js:35:1)
    at renderWithHooks (react-dom.development.js:16175:1)
    at mountIndeterminateComponent (react-dom.development.js:20913:1)
    at beginWork (react-dom.development.js:22416:1)
    at HTMLUnknownElement.callCallback (react-dom.development.js:4161:1)
    at Object.invokeGuardedCallbackDev (react-dom.development.js:4210:1)
    at invokeGuardedCallback (react-dom.development.js:4274:1)
    at beginWork$1 (react-dom.development.js:27405:1)
    at performUnitOfWork (react-dom.development.js:26513:1)
    at workLoopSync (react-dom.development.js:26422:1)

How can it suddenly be unable to read Custom Post Type on WordPress when I was making the exact same reference as before except in the JSX?

score 0 · Accepted Answer · answered Jul 09 '22 at 09:04

The issue was due to order of operations

data is undefined while the query is still loading or has an error, here is the correct syntax:

Cannot destructure GraphQL query as apollo-client is undefined?

I have also revised my technique within this answer to de-structure the object correctly

Why does GraphQL reference crash when embedded in Object vs JSX?

1 Answers1