GraphQL嵌套结构Mutation问题：实现addEntity函数遇阻

Alright, let's tackle this nested data issue with your addEntity mutation. Since your queries are working fine, the problem is almost certainly in how you're defining your mutation schema or handling the nested primaryContact data in your resolver. Let's walk through the fixes step by step.

1. Fix Your Mutation Schema Definition #

First, make sure you've properly defined input types for the nested data, and that your mutation accepts this structured input. Here's how to structure it correctly:

# Define the nested contact input type
input PrimaryContactInput {
  name: String!
  email: String!
  phone: String # Optional field
}

# Define the main entity input type that includes the nested contact
input EntityInput {
  name: String!
  description: String
  primaryContact: PrimaryContactInput! # Mark as required since you're including it
}

# Define the output types to match the data structure
type PrimaryContact {
  name: String!
  email: String!
  phone: String
}

type Entity {
  id: ID!
  name: String!
  description: String
  primaryContact: PrimaryContact!
}

# Update your Mutation type to use the EntityInput
type Mutation {
  addEntity(input: EntityInput!): Entity
}

The key here is matching the input structure to the output structure so GraphQL knows how to validate and return the nested data.

2. Correct Your addEntity Resolver Logic #

Next, ensure your resolver properly passes the nested data to json-server via axios. Json-server supports nested objects out of the box, so you don't need to do any special transformation—just send the full input object:

const axios = require('axios');

// Inside your resolvers object
const resolvers = {
  // ... your existing query resolvers
  addEntity: async (parent, { input }) => {
    try {
      // Send the entire input (including nested primaryContact) to json-server
      const response = await axios.post('http://localhost:3000/entities', input);
      return response.data;
    } catch (error) {
      // Throw a clear error for debugging
      throw new Error(`Failed to create entity: ${error.response?.data || error.message}`);
    }
  }
};

Double-check that your json-server endpoint is correct (adjust the URL if your server runs on a different port).

3. Validate Your GraphQL Server Setup #

Make sure your express-graphql entry point correctly links your schema and resolvers. Here's a minimal working example:

const express = require('express');
const { graphqlHTTP } = require('express-graphql');
const { buildSchema } = require('graphql');
const resolvers = require('./resolvers'); // Import your resolvers

// Build the schema using the definition from step 1
const schema = buildSchema(`
  input PrimaryContactInput {
    name: String!
    email: String!
    phone: String
  }

  input EntityInput {
    name: String!
    description: String
    primaryContact: PrimaryContactInput!
  }

  type PrimaryContact {
    name: String!
    email: String!
    phone: String
  }

  type Entity {
    id: ID!
    name: String!
    description: String
    primaryContact: PrimaryContact!
  }

  type Query {
    # Add your existing query resolvers here
    getEntity(id: ID!): Entity
  }

  type Mutation {
    addEntity(input: EntityInput!): Entity
  }
`);

const app = express();
app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: resolvers,
  graphiql: true, // Enable GraphiQL for easy testing
}));

app.listen(4000, () => {
  console.log('GraphQL server running at http://localhost:4000/graphql');
});

4. Troubleshoot Common Errors #

If you're still seeing issues, check for these common pitfalls:

• Input/Output Type Mismatch: Ensure the fields in PrimaryContactInput match exactly with PrimaryContact (e.g., don't mark a field as required in the output but optional in the input).
• Json-Server Configuration: Make sure your db.json has an empty entities array to start with:

  {
    "entities": []
  }
  

• Axios Headers: Axios automatically sets Content-Type: application/json, but if you've overridden headers, double-check this is present.
• Error Messages: Use the error details from GraphiQL—if it says "Field 'primaryContact' of type 'PrimaryContactInput!' must not be null", you're likely not passing the nested data correctly in your mutation test.

5. Test the Mutation in GraphiQL #

Use this test mutation to verify everything works:

mutation AddNewEntity {
  addEntity(input: {
    name: "Acme Corp",
    description: "A test company",
    primaryContact: {
      name: "Jane Smith",
      email: "jane@acme.com",
      phone: "555-1234"
    }
  }) {
    id
    name
    primaryContact {
      name
      email
    }
  }
}

If successful, you should get back the new entity with its nested primary contact data.

内容的提问来源于stack exchange，提问作者trueCodian