CODEWITHSUNDEEP
typescript
lzszone
lzszone

Reputation: 75

Type not match? "...is missing the following properties from type..."

I want to do 2 things: 1: Dynamically import package with the name 2: Assert the type of the package(I know what will it return)

type Task = [
  Object, 
  Function
];

const getTasks: Promise<Task[]> = async (names: Array<string>) => {
  const pkgs = names.map(name => import(name) as Promise<Task>);
  return Promise.all(pkgs)
}

Error output:

Type '(names: string[]) => Promise<[Object, Function][]>' is missing the following properties from type 'Promise<[Object, Function][]>': then, catch, [Symbol.toStringTag], finallyts(2739)
index.ts(55, 35): Did you mean to call this expression?

Typescript: 3.3.3

Upvotes: 3

Views: 9090

Answers (2)

Devansh J
Devansh J

Reputation: 4224

Umm I guess a small typo? You probably meant to write this...

const getTasks = async (names: Array<string>): Promise<Task[]> => { ... }

Upvotes: 1

SpencerPark
SpencerPark

Reputation: 3506

Did you mean to call this expression? in the error message is suggesting that a function is in a place where a value is expected. getTasks is declared to be a Promise but the expression on the right hand side is a function.

There are 2 options depending on what the intention was. Either immediately invoke the function:

const getTasks: Promise<Task[]> = (async (names: Array<string>) => {
    const pkgs = names.map(name => import(name) as Promise<Task>);
    return Promise.all(pkgs)
})(['package-1', 'package-2']);

or (like the name getTasks suggests) fix the type to reflect that getTasks is a function:

const getTasks: (names: Array<String>) => Promise<Task[]> = async (names: Array<string>) => {
    const pkgs = names.map(name => import(name) as Promise<Task>);
    return Promise.all(pkgs)
}
// or
const getTasks = async (names: Array<string>): Promise<Task[]> => {
    const pkgs = names.map(name => import(name) as Promise<Task>);
    return Promise.all(pkgs)
}

Upvotes: 6

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