No overload matches this call. Overload 1 of 2, '(...items: ConcatArray<never>[]): never[-CodePudding

Making recursive comment structure, I use the following function.

 interface IComment {
      _id: string;
      body: string;
      forum_id: string;
      parent_comment_id: string;
      author_name: string;
      author_id: string;
      authorPic: string;
      votes: number;
      h_voted: number;
      created_at: string;
      updated_at: string;
    }
    
    const getCommentsWithChildren = (comments: IComment[]) => {
      
      const commentsWithChildren = comments.map((comment) => ({
        ...comment,
        children: [],// This is new empty child array
      }));
      commentsWithChildren.forEach((childComment) => {
        const { parent_comment_id } = childComment;
        if (parent_comment_id) {
          const parent = commentsWithChildren.find(
            (comment) => parent_comment_id === comment._id
          );
          if (parent !== undefined) {
            parent.children = parent.children.concat(childComment);// This part make the error
          }
        }
      });
      return commentsWithChildren.filter(
        ({ parent_comment_id, body, children }) =>
          parent_comment_id === null && (body !== null || children.length > 0)
      );
    };

As you can see, to make a child object array, add 'children: []'

and then in recursive function add child by

'parent.children = parent.children.concat(childComment);'

above line cause the error

'No overload matches this call. Overload 1 of 2, '(...items: ConcatArray[]): never[]', gave the following error.

Argument of type '{ children: never[]; _id: string; body: string; forum_id: string; parent_comment_id: string; author_name: string; author_id: string; authorPic: string; votes: number; h_voted: number; created_at: string; updated_at: string; }' is not assignable to parameter of type 'ConcatArray'.

Type '{ children: never[]; _id: string; body: string; forum_id: string; parent_comment_id: string; author_name: string; author_id: string; authorPic: string; votes: number; h_voted: number; created_at: string; updated_at: string; }' is missing the following properties from type 'ConcatArray': length, join, slice

Overload 2 of 2, '(...items: ConcatArray[]): never[]', gave the following error.

maybe 'children: []' is never type...

In typescript, how to solve this problem? thanks very much for reading this writing.

CodePudding user response：

When you create your empty array within commentsWithChildren you create an array of never[] - which is what cannot be concatenated.

You should explicitly set the type of commentsWithChildren or the array you set to commentsWithChildren.children.

CodePudding user response：

Thank your N.J.Dawson!!

I solved the above error.

The following code is that.

interface IComment {
  _id: string;
  body: string;
  forum_id: string;
  parent_comment_id: string;
  author_name: string;
  author_id: string;
  authorPic: string;
  votes: number;
  h_voted: number;
  created_at: string;
  updated_at: string;
}

interface ICommentWithChildren extends IComment {
  children: IComment[];
}

const getCommentsWithChildren = (comments: IComment[]) => {
  const commentsWithChildren: ICommentWithChildren[] = comments.map(
    (comment) => ({
      ...comment,
      children: [],
    })
  );
  commentsWithChildren.forEach((childComment) => {
    const { parent_comment_id } = childComment;
    if (parent_comment_id) {
      const parent = commentsWithChildren.find(
        (comment) => parent_comment_id === comment._id
      );
      if (parent !== undefined) {
        parent.children = parent.children.concat(childComment);
      }
    }
  });
  return commentsWithChildren.filter(
    ({ parent_comment_id, body, children }) =>
      parent_comment_id === null && (body !== null || children.length > 0)
  );
};

added part is

interface ICommentWithChildren extends IComment {
  children: IComment[];
}

and modified part is

const commentsWithChildren: ICommentWithChildren[]

thanks again!!