clarencenpy

const typeDefs = gql`
  # define wrapper result type that could return either
  # the added Event on success, or an array of Errors 
  # on error. Notice both fields are nullable. 
  type AddEventResult {
    event: Event
    validationErrors: [FieldValidationError!]
  }

  # define how you want errors to be represented. This

clarencenpy

const typeDefs = gql`
  type Event {
    name: String!
    date: Date!
    capacity: Int!
    zipCode: String!
  }
`;

clarencenpy

import ApolloClient from 'apollo-boost';

const client = new ApolloClient({
  uri: '<your graphql endpoint>',
  // Apollo Boost allows you to specify a custom error link for your client
  onError: ({ graphQLErrors, networkError, operation, forward }) => {
    if (graphQLErrors) {
      for (let err of graphQLErrors) {
        // handle errors differently based on its error code
        switch (err.extensions.code) {

clarencenpy

{
  "message": "Failed to get events due to validation errors",
  "extensions": {
    "code": "BAD_USER_INPUT",
    "exception": {
      "validationErrors": {
        "zipCode": "This is not a valid zipcode"
      }
    }
  }

clarencenpy

import { UserInputError } from 'apollo-server';

const resolvers = {
  Query: {
    events(root, { zipCode }) {
      
      // do custom validation for user inputs
      const validationErrors = {};
      if (!isValidZipCode(zipCode)) {
        validationErrors.zipCode = 'This is not a valid zipcode';