Nest JS GraphQL “Cannot return null for non-nullable” [duplicate]

问题

I tried to resolve one error in my study code, but failed. Then I just try to launch this code...

https://github.com/nestjs/nest/tree/master/sample/23-type-graphql

and the same situation...

Error looks like

{
  "errors": [
    {
      "message": "Cannot return null for non-nullable field Recipe.id.",
      "locations": [
        {
          "line": 3,
          "column": 5
        }
      ],
      "path": [
        "recipe",
        "id"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "Error: Cannot return null for non-nullable field Recipe.id.",
            "    at completeValue (/home/innistry/Downloads/nest-master/sample/23-type-graphql/node_modules/graphql/execution/execute.js:560:13)",
            "    at /home/innistry/Downloads/nest-master/sample/23-type-graphql/node_modules/graphql/execution/execute.js:492:16",
            "    at process._tickCallback (internal/process/next_tick.js:68:7)"
          ]
        }
      }
    }
  ],
  "data": null
}

Has someone ideas?

回答1:

Make the property nullable or make sure you don't return null as the value.

回答2:

This is the fastest fix, just to launch.

import { Field, ID, ObjectType } from 'type-graphql';

@ObjectType()
export class Recipe {
  @Field(type => ID, { nullable: true })
  id?: string;

  @Field({ nullable: true })
  title?: string;

  @Field({ nullable: true })
  description?: string;

  @Field({ nullable: true })
  creationDate?: Date;

  @Field(type => [String], { nullable: true })
  ingredients?: string[];
}

来源：https://stackoverflow.com/questions/58140891/nest-js-graphql-cannot-return-null-for-non-nullable

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