Improve class typing

[tranquil marsh]

• Consider reading #how-to-get-help to improve your question!
• Explain what exactly your issue is.
• Post the full error stack trace, not just the top part!
• Show your code!
• Issue solved? Press the button!
• ✅ Marked as resolved by OP

[hazy pilot]

you can't

[candid pond]

You can have 2 classes

class StartedMatch {
  public constructor(public data: MatchData) {}
}

class UnstartedMatch {
  public async start() {
    const data = await create();
    return new StartedMatch(data);
  }
}

type Match = StartedMatch | UnstartedMatch;

let match: Match = new UnstartedMatch();
match = await match.start();

match.data

Another way with an interface

interface StartedMatch {
  data: MatchData;
}

class Match {
  public constructor(public data?: MatchData) {}

  public async start() {
    const data = await create();
    return new StartedMatch(data);
  }

  public isStarted(): this is StartedMatch {
    return typeof this.data !== 'undefined';
  }
}

const match = new Match();
await match.start();

if (match.isStarted()) {
  match.data;
}