I want to construct type {name:string,value:string} from another type Todo.

Below code throws error: Property '0' does not exist on type 'Pick<Todo, "items">'.

type Todo = {
  title: string;
  items:Array<{name:string,value:string}>;
  description: string;
  completed: boolean;
}
 
type TodoItems = Pick<Todo, "items">[0]; //ERROR: Property '0' does not exist on type 'Pick<Todo, "items">'.
 
const todo: TodoItems = {
  name: "Clean room",
  value: "yes",
};

Note: Todo comes from a ts module so it's not editable.

What approach could I follow to extract {name:string,value:string} from Todo?

CodePudding user response：

I think you need to split Todo item into separate type as Dmitrii Zolotuhin said, it will be the rightest way. BUT if you can't do it, you can create this type

type TodoItems = Todo["items"][number]
// ...or
type TodoItems = Pick<Todo, "items">["items"][number]

Typescript playground

CodePudding user response：

You were almost right, try type TodoItems = Todo["items"][0];

type Todo = {
  title: string;
  items:Array<{name:string,value:string}>;
  description: string;
  completed: boolean;
}
 
type TodoItems = Todo["items"][0]; 
//... 

Playground Link

CodePudding user response：

I would do it in the other way:

interface TodoItem {
    name: string
    value: string
}

interface Todo {
    title: string
    items: TodoItem[]
    description: string
    completed: boolean
}

const todo: TodoItem = {
    name: "Clean room",
    value: "yes",
}