Used with Persisted Caching (JSON string from LocalStorage, AsyncStorage etc)

[woltob]

Hi all,

if you want to revive your custom scalars from the persisted Cache (https://github.com/apollographql/apollo-cache-persist) (where it is saved as stringified JSON), you can use the JSON.parse function with a revive method.

I am using it as such:

import { DateTime } from 'luxon';

// Works for keys like createdAt, updatedAt and timestamp.
export const parseJsonWithDateTime = (
  jsonString: string,
  keyCheckFunctions: Array<(key: string) => boolean> = [
    (key) => key === 'timestamp',
    (key) => key.endsWith('At'),
  ],
) => {
  return JSON.parse(jsonString, (key, value) => {
    for (const keyCheckFunction of keyCheckFunctions) {
      if (keyCheckFunction(key)) {
        return DateTime.fromISO(value);
      }
    }
  });
};

To enable custom scalar type generation with the newest apollo codegen, you can use the following setup for codegen.yml

I am not so sure about the two options here
passthroughCustomScalars: true and customScalarFormat: 'passthrough' but they don't break it.

hooks:
  afterAllFileWrite:
    - prettier --write
overwrite: true
schema: 'graphql.schema.json'
documents: 'src/**/*.{tsx,ts}'
config:
  scalars:
    DateTime: DateTime
    JSONObject: JSONObject
generates:
  src/generated-graphql-types.tsx:
    plugins:
      - 'typescript'
      - 'typescript-operations'
      - 'typescript-react-apollo'
      - 'named-operations-object'
    config:
      namingConvention:
        default: 'no-change-case'
        enumValues: 'keep'
      passthroughCustomScalars: true
      customScalarFormat: 'passthrough'
      withComponent: false
      withHOC: true
  ./src/generated-graphql-fragment-matcher.ts:
    plugins:
      - fragment-matcher
    config:
      namingConvention:
        default: 'no-change-case'
        enumValues: 'keep'
      passthroughCustomScalars: true
      customScalarFormat: 'passthrough'
  ./graphql.schema.json:
    plugins:
      - 'introspection'
    config:
      passthroughCustomScalars: true
      customScalarFormat: 'passthrough'
      namingConvention:
        default: 'no-change-case'
        enumValues: 'keep'

Hope it helps someone.

[eturino]

I'll try it out. Thanks!