Is there a method to define an 'internal' property within a TypeScript type?

I created a custom 'library' in Angular and TypeScript. This library is distributed as a *.ts package within other Angular workspaces.

Within this library, I have an exported class that contains various properties.
One specific property in this class should only be set within the library itself.

TypeScript Code Example:

export class Bar{
   foo:boolean; // to be set exclusively within the library scope
}

Is there a method to declare a property as 'internal' in TypeScript, or any alternative way to restrict a property to only be set within the library?

angulartypescript

Answer №1

If you're looking to create a read-only property that can only be modified within the library itself, there is a workaround available.

It may not be the most elegant solution but it gets the job done:

  1. Create a class that is not exposed outside of the library.
export class Restricted{
    data!:string;
}
  1. Add a 'Readonly' property in the main exported class.
export class Accessible{
    Restricted?:Readonly<Restricted>=new Restricted();
}
  1. Set the property internally within the library like this:
let accessible:Accessible=new Accessible();
(accessible.Restricted as Restricted).data="example";
  1. External attempts to modify the property will fail.

Error: Cannot find name 'Restricted'.ts(2304)

Error: Cannot assign to 'data' because it is a read-only property.ts(2540)

https://i.stack.imgur.com/jeD7z.png

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