Typescript interface, using string constants for properties

Question

I recently encountered the following design-issue when trying to describe a Notification-format (and formats in general) with a Typescript interface.

Context: Notificati

Answer 1

You can use the Record<TKey, TValue> type to define the interface:

type TextType = "Text"; // or "Message" if format changes later
type TitleType = "Title";
type PriorityType = "Priority";
type Notification = Partial<Record<typeof TextType | typeof TitleType, string>
        & Record<typeof PriorityType, number>>;

let notif: Notification;

let t = notif[TextType] // Will be string
let t2 = notif.Text // Also works 

The problem is there is no compiler way to enforce that access happens using the string constant, you could still access with .

Note

On typescript 2.7 and newer you can also do:

const TextType = "Text"; // or "Message" etc
const TitleType = "Title";
const PriorityType = "Priority";

interface Notification {
    [TextType]?: string
    [TitleType]?: string
    [PriorityType]?: number
}

But the same problem still applies of access