Defining preset values within a TypeScript model class

Question

Defining preset values within a TypeScript model class

Suppose I have a User class and I want to instantiate only predefined 'status'. Is this the optimal approach? Are there any other alternatives? What is the correct way to achieve this? Thank you in advance.

export class User {
    constructor(
        username: string,
        email: string,
        status: AccountStatus
    ){}
}

export enum AcountStatus {
    Active = 'Active',
    Suspended = 'Suspended'
}

import { User } from 'app/models/user.model'
import { AccountStatus } from 'app/models/user.model'

private user: User;

this.user = new User('username', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="f580869087b580869087db9698">[email protected]</a>', AccountStatus.Active)

javascript typescript

Answer 1

Answer №1

If the majority of users are expected to have an initial status of Active, you can set a default value for the status in the constructor like this:

class User {
  constructor(
    public username: string,
    public email: string,
    public status: AccountStatus = AccountStatus.Active
  ){}
}

This way, when creating a new Active user, you don't have to specify the status each time:

let user: User;

user = new User('username', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dfaaacbaad9faaacbaadf1bcb2">[email protected]</a>')

Try it out on the playground.

Another approach you can take for improvement is to use a union type instead of the AccountStatus enum:

class User {
    constructor(
      public username: string,
      public email: string,
      public status: 'Active' | 'Suspended' = 'Active'
    ){}
}

let user = new User('username', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a1d4d2c4d3e1d4d2c4d38fc2cc">[email protected]</a>')

Answer 2

If the majority of users are expected to have an initial status of Active, you can set a default value for the status in the constructor like this:

class User {
  constructor(
    public username: string,
    public email: string,
    public status: AccountStatus = AccountStatus.Active
  ){}
}

This way, when creating a new Active user, you don't have to specify the status each time:

let user: User;

user = new User('username', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dfaaacbaad9faaacbaadf1bcb2">[email protected]</a>')

Try it out on the playground.

Another approach you can take for improvement is to use a union type instead of the AccountStatus enum:

class User {
    constructor(
      public username: string,
      public email: string,
      public status: 'Active' | 'Suspended' = 'Active'
    ){}
}

let user = new User('username', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a1d4d2c4d3e1d4d2c4d38fc2cc">[email protected]</a>')

Answer 3

Answer №2

If you're looking to provide more flexibility to the user of your code, you have the option to accept either a union of string literals or a member from your string enum:

TS Playground

type Values<T> = T[keyof T];
type StringEnumToUnion<T extends Record<string, string>> = `${Values<T>}`;

function valueIsStringEnum <Enum extends Record<string, string>>(
  value: unknown,
  o: Enum,
): value is Values<Enum> {
  return Object.values(o).includes(value as string);
}

function assert (expr: unknown, msg?: string): asserts expr {
  if (!expr) throw new Error(msg);
}

export enum AccountStatus {
  Active = 'Active',
  Suspended = 'Suspended',
}

export class User {
  constructor (
    username: string,
    email: string,
    status: StringEnumToUnion<typeof AccountStatus>,
  ) {
    let ac: AccountStatus;

    ac = status; /*
    ~~
    Type '"Active" | "Suspended"' is not assignable to type 'AccountStatus'.
      Type '"Active"' is not assignable to type 'AccountStatus'.(2322) */

    // Assert it back to AccountStatus for your own usage if you want:
    assert(valueIsStringEnum(status, AccountStatus));
    ac = status; // ok
  }
}


// Example usage:

new User('user', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dca9afb9ae9cb2bdb1b9f2a8b0b8">[email protected]</a>', 'ACTUVE'); /*
                                  ~~~~~~~~
Argument of type '"ACTUVE"' is not assignable to parameter of type '"Active" | "Suspended"'.(2345) */

new User('user', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="cbbeb8aeb98ba5aaa6aee5bfa7af">[email protected]</a>', 'Active'); // ok
new User('user', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="582d2b3d2a183639353d762c34

Answer 4

If you're looking to provide more flexibility to the user of your code, you have the option to accept either a union of string literals or a member from your string enum:

TS Playground

type Values<T> = T[keyof T];
type StringEnumToUnion<T extends Record<string, string>> = `${Values<T>}`;

function valueIsStringEnum <Enum extends Record<string, string>>(
  value: unknown,
  o: Enum,
): value is Values<Enum> {
  return Object.values(o).includes(value as string);
}

function assert (expr: unknown, msg?: string): asserts expr {
  if (!expr) throw new Error(msg);
}

export enum AccountStatus {
  Active = 'Active',
  Suspended = 'Suspended',
}

export class User {
  constructor (
    username: string,
    email: string,
    status: StringEnumToUnion<typeof AccountStatus>,
  ) {
    let ac: AccountStatus;

    ac = status; /*
    ~~
    Type '"Active" | "Suspended"' is not assignable to type 'AccountStatus'.
      Type '"Active"' is not assignable to type 'AccountStatus'.(2322) */

    // Assert it back to AccountStatus for your own usage if you want:
    assert(valueIsStringEnum(status, AccountStatus));
    ac = status; // ok
  }
}


// Example usage:

new User('user', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dca9afb9ae9cb2bdb1b9f2a8b0b8">[email protected]</a>', 'ACTUVE'); /*
                                  ~~~~~~~~
Argument of type '"ACTUVE"' is not assignable to parameter of type '"Active" | "Suspended"'.(2345) */

new User('user', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="cbbeb8aeb98ba5aaa6aee5bfa7af">[email protected]</a>', 'Active'); // ok
new User('user', '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="582d2b3d2a183639353d762c34

Defining preset values within a TypeScript model class

Answer №1

Answer №2

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