GraphQL/Apollo-Server-Express 错误：不能为不可为空的字段返回 null 突变数据：null答案

【问题标题】：GraphQL/Apollo-Server-Express Error: Cannot return null for non-nullable field Mutation Data: nullGraphQL/Apollo-Server-Express 错误：不能为不可为空的字段返回 null 突变数据：null
【发布时间】：2021-10-07 09:24:39
【问题描述】：

到目前为止，除了这个之外，所有测试过的查询和突变都可以正常工作。

我在阿波罗游乐场收到此错误。

“消息”：

Cannot return null for non-nullable field Mutation.createComment
...

“扩展”：

...
Data: null

如果不是所有我能找到的 google 和 stackoverflow 解决方案，我已经尝试了大部分，现在我正在寻求帮助。非常感谢我能得到解决此问题的任何帮助。

后模型：

const postSchema = new Schema({
  body: String,
  username: String,
  createdAt: String,
  comments: [
    {
      body: String,
      username: String,
      createdAt: String,
    },
  ],
  likes: [
    {
      username: String,
      createdAt: String,
    },
  ],
  // Linking the user model
  user: {
    type: Schema.Types.ObjectId,
    ref: "users",
  },
});

评论解析器：

Mutation: {
    createComment: async (_, { postId, body, username }, context) => {
      const { username } = checkAuth(context);
      if (body.trim === "") {
        throw new UserInputError("Empty comment", {
          errors: {
            body: "Comment body can not be empty",
          },
        });
      }

      const post = await Post.findById(postId);

      if (post) {
        post.comments.unshift({
          body,
          username,
          createdAt: new Date().toISOString(),
        });
        await post.save();
        return post;
      } else throw new UserInputError("Post not found");
},

类型定义：

  type Post {
    id: ID!
    body: String!
    createdAt: String!
    username: String!
    comments: [Comment]!
    likes: [Like]!
    likeCount: Int!
    commentCount: Int!
  }
  type Comment {
    id: ID!
    createdAt: String!
    username: String!
    body: String!
  }
  type Like {
    id: ID!
    createdAt: String!
    username: String!
  }
  type User {
    id: ID!
    email: String!
    token: String!
    username: String!
    createdAt: String!
    confirmed: Boolean!
  }
  input RegisterInput {
    username: String!
    password: String!
    confirmPassword: String!
    email: String!
  }
  type Query {
    getUsers: [User]
    getPosts: [Post]
    getPost(postId: ID!): Post
  }
  type Mutation {
    register(registerInput: RegisterInput): User!
    login(email: String!, password: String!): User!
    createPost(body: String!): Post!
    deletePost(postId: ID!): String!
    createComment(postId: ID!, body: String!, username: String!): Post!
    deleteComment(postId: ID!, commentId: ID!): Post!
    likePost(postId: ID!): Post!
  }
  type Subscription {
    newPost: Post!
  }

我在 Apollo Playground 中使用的变异：

mutation createComment{
  createComment(
    postId: "6106db3a0e9e783e98b996a4", 
    body: "This is a new comment", 
    username: "Random user"
) {
  id
  comments {
    id
    body
    createdAt
    username
  }
  commentCount
}

}

【问题讨论】：

标签： graphql apollo-server

【解决方案1】：

在无休止地尝试了网络上所有可用的解决方案之后，实际上我的 index.js 文件中的 graphql 解析器出现了导入错误。

我有 const cmetsResolvers = require("./users");

什么时候应该是 const cmetsResolvers = require("./cmets");

【讨论】：