Conditional Type

[sick umbra]

export interface IUser {
  _id?: ObjectId
  id: idType;
  username: string
  email: string
  password: string
  profilePic?: string
  contributions?: number
  rate?: number
  bio?: string
}```

I would like to update the definition of the id field based on the value of the DB_TYPE environment variable. If DB_TYPE is set to 'sql', the type of the id field should be string. Otherwise, if DB_TYPE is set to 'mongodb' or is not defined, the type of the id field should be never. How can I achieve this?

[silk spear]

not possible

environment variables are dynmaic and can't be known at compile time

I suggest creating different variations of that IUser type
and create a union for all variations
then use a type predicate function to pick the right type where you need it

also, on a sidenote, it's not a common thing to name your interfafes with a leading I
just use the "normal" name directly

[sick umbra]

Thanks for your clarification ..
can u show me the code

[twilit rapids]

Ascor8522#7606

Playground Link

Preview:```ts
import {} from "node:process"
import {ObjectId} from "mongodb"

////////////////////// The types for the application

interface SQLUser extends PartialUser {
id: string
}

interface NoSQLUser extends PartialUser {
_id?: ObjectId
}

interface
...```

You can choose specific lines to embed by selecting them before copying the link.

[silk spear]

@sick umbra

but tbh, I probably wounld't do that

the id part of your type is specific to the db you use

and the model (classes and types) of your app shouldn't have to deal with that

you should create types that work for any kind of db, and only deal with those spefici fields when saving of retrieving data from or to the database

[sick umbra]

  const user: IUser = {
    id: crypto.randomUUID(), // generate uuid if dbType = sql
    username,
    email,
    password: hashPassword(password!),
    bio,
    socialLinks,
    interests,
    profilePic,
    activity: {
      problems: [],
      solutions: [],
      reacts: [],
    },
    createdAt: new Date(),
    updatedAt: new Date(),
  }

This is the structure of user