Currently, I am working on creating an unchangeable, nested data structure that also incorporates inheritance. To achieve this, I am using the Readonly generic type. In order to create different types within this structure, one of these Readonly types needs to extend another.
type Person = Readonly<{
name : string
}>
type Student = Readonly<{
school : string
}>
My goal is for the Student type to inherit from the Person type and maintain the readonly name property.
Here is a possible solution
const User = Readonly<{
username : string
}>
const Admin = User & Readonly<{
role : string
}>
function updateUser(a: Admin) {
a.username = "" // this line will throw an error
a.role = "admin" // this line will also throw an error
}
To achieve this, you will need to create an intermediate interface called InternalStudent, which extends the Person interface.
type Person = Readonly<{
name: string
}>
interface InternalStudent extends Person {
school: string
}
type Student = Readonly<InternalStudent>;
let student: Student = { school: '1', name: '2' } // This is valid
student.name = '1'; // This will result in an error
student.school = '2'; // This will also result in an error
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