CODEWITHSUNDEEP
typescripttypescript2.0
POV
POV

Reputation: 12025

Union type in Typescript?

Why this defination of type is not allowed in TypeScript?

type profileType = 'TEACHER' | 'PRINCIPAL';

interface FormList {
    [ key: profileType ] : IForm[];
}

let forms: FormList;

forms = {
    'TEACHER' : [{ id: 1, name: "o" }, { id: 1, name: "b" }]
}

It invokes an error in line: [ key: profileType ] : IForm[];.

Upvotes: 0

Views: 81

Answers (1)

Aleksey L.
Aleksey L.

Reputation: 38046

You can map string literals from union into new type. This is called mapped type in typescript:

type IForm = {};
type ProfileType = 'TEACHER' | 'PRINCIPAL';    

type FormList = { [P in ProfileType]: IForm[] };

let forms: FormList;

forms = {
    'TEACHER': [{ id: 1, name: "o" }, { id: 1, name: "b" }],
    'PRINCIPAL': [{ id: 1, name: "o" }, { id: 1, name: "b" }]
}

Upvotes: 1

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