How do I declare a type for array object using 'Pick' and '&' keyword at the sam-CodePudding

I'm very new to TypeScript and what I want is declare a type for array object just like below.

const temp = [{
  id: 0, // number
  follower_id: 0, // number
  followee_id: 0, // number
  created_at: '', // string 
  delete_at: '', // string
}, {
  id: 1,
  follower_id: 1,
  followee_id: 0,
  created_at: '',
  delete_at: '',
}];

I can make a new type for the temp array but I just wanna reuse the type that I defined before so that I can avoid repeating meaningless typing. So, here are the types that I made. Two interface for the userStateType.

interface IUserInfo {
  id: number;
  created_at: string;
  deleted_at: string | null;
  username: string;
  description: string;
  image_url: string;
  name: string;
  updated_at: string;
}

interface IFollows {
  follower_id: number,
  followee_id: number
}

and I tried to write down my UserStateType like below.

type UserStateType = {
  userInfo: IUserInfo | null
  followers: Pick<IUserInfo, 'created_at' | 'deleted_at'> & IFollows | null
};

But followers in UserStateType has to be an array type not an object type so type error occurs. (Currently, I'm using this type to avoid type error. followers: [] | null)

I can't even use [] because I used not only Pick keyword but & over there.

In this situation, how do I come up with efficient solution?

If my explanation is not clear enough, please comment!

CodePudding user response：

You're very close. You just need to make it an array:

followers: (Pick<IUserInfo, 'created_at' | 'deleted_at'> & IFollows)[] | null

Or you could make a Follower type and use that:

type Follower = Pick<IUserInfo, 'created_at' | 'deleted_at'> & IFollows;

type UserStateType = {
  userInfo: IUserInfo | null;
  followers: Follower[] | null;
};

CodePudding user response：

You're just missing brackets:

interface IUserInfo {
    id: number;
    created_at: string;
    deleted_at: string | null;
    username: string;
    description: string;
    image_url: string;
    name: string;
    updated_at: string;
}

interface IFollows {
    follower_id: number,
    followee_id: number
}

type UserStateType = {
    userInfo: IUserInfo | null
    followers: (Pick<IUserInfo, 'created_at' | 'deleted_at'> & IFollows)[]
};

and then you can do:

const example:UserStateType = { followers:{created_at:'',deleted_at:'',followee_id:0,follower_id:0}], userInfo:null}