I've a lot of tables in Lovefield and their respective Interfaces for what columns they have.
Example:
export interface IMyTable {
id: number;
title: string;
createdAt: Date;
isDeleted: boolean;
}
I'd like to have the property names of this interface in an array like this:
const IMyTable = ["id", "title", "createdAt", "isDeleted"];
I cannot make an object/array based on the interface IMyTable directly which should do the trick because I'd be getting the interface names of the tables dynamically. Hence I need to iterate over these properties in the interface and get an array out of it.
How do I achieve this result?
As of TypeScript 2.3 (or should I say 2.4, as in 2.3 this feature contains a bug which has been fixed in typescript@2.4-dev), you can create a custom transformer to achieve what you want to do.
Actually, I have already created such a custom transformer, which enables the following.
https://github.com/kimamula/ts-transformer-keys
import { keys } from 'ts-transformer-keys';
interface Props {
id: string;
name: string;
age: number;
}
const keysOfProps = keys<Props>();
console.log(keysOfProps); // ['id', 'name', 'age']
Unfortunately, custom transformers are currently not so easy to use. You have to use them with the TypeScript transformation API instead of executing tsc command. There is an issue requesting a plugin support for custom transformers.
Maybe it's too late, but in version 2.1 of TypeScript you can use keyof to get the type like this:
interface Person {
name: string;
age: number;
location: string;
}
type K1 = keyof Person; // "name" | "age" | "location"
type K2 = keyof Person[]; // "length" | "push" | "pop" | "concat" | ...
type K3 = keyof { [x: string]: Person }; // string
The following requires you to list the keys on your own, but at least TypeScript will enforce IUserProfile and IUserProfileKeys have the exact same keys (Required<T> was added in TypeScript 2.8):
export interface IUserProfile {
id: string;
name: string;
};
type KeysEnum<T> = { [P in keyof Required<T>]: true };
const IUserProfileKeys: KeysEnum<IUserProfile> = {
id: true,
name: true,
};