Currently, I am delving into the world of Typescript and have been exploring various exercises that I stumbled upon online. However, I have encountered some trouble with the feedback on incorrect solutions. Specifically, I am facing an issue with the following code snippet where TS is constantly flagging that the property type is not defined on T:
interface User {
type: 'user';
name: string;
age: number;
occupation: string;
}
interface Admin {
type: 'admin';
name: string;
age: number;
role: string;
}
export type Person = User | Admin;
export const persons: Person[] = [
{ type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
{ type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
{ type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' },
{ type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' },
{ type: 'user', name: 'Wilson', age: 23, occupation: 'Ball' },
{ type: 'admin', name: 'Agent Smith', age: 23, role: 'Anti-virus engineer' }
];
export function filterPersons<T>(persons: T[], personType: string, criteria: T): T[] {
return persons
.filter((person) => person.type === personType)
.filter((person) => {
let criteriaKeys = Object.keys(criteria) as (keyof T)[];
return criteriaKeys.every((fieldName) => {
return person[fieldName] === criteria[fieldName];
});
});
}
export const usersOfAge23 = filterPersons<User>(persons, 'user', { age: 23 });
export const adminsOfAge23 = filterPersons<Admin>(persons, 'admin', { age: 23 });
I am a bit confused on what I might be doing wrong here. Shouldn't T be a generic type or in this case User or Admin that is passed accordingly?