CODEWITHSUNDEEP
typescript
Slevin
Slevin

Reputation: 4222

How to extract a Union from an Array

I'm using graphql-code-generator to generate TypeScript definitions from my GraphQL queries and currently trying to extract a specific union from an array. Is this possible in TypeScript? I've found an example where someone extracted a type from a generic and tried to make use if the Extract function, but this does not work and returns just never:

export type Foo = Array<(
    {
      id: string;
      __typename: 'Data1'
    }
    | {
      id: string;
      __typename: 'Data2'
    }
  )>;

type MyQueryData1 = Extract<Foo, { __typename: "Data1"}>
type MyQueryData2 = Extract<Foo, { __typename: "Data2"}>

TypeScript Playground

Upvotes: 0

Views: 153

Answers (1)

subashMahapatra
subashMahapatra

Reputation: 6837

Is this the result you want? ts playground

If so you have to extract the type from the deirved union type from the element values of the array,

type MyQueryData1 = Extract<Foo[number], { __typename: "Data1"}>
type MyQueryData2 = Extract<Foo[number], { __typename: "Data2"}>

Upvotes: 1

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