TypeScript exercises 3번 문제

interface User {
    name: string;
    age: number;
    occupation: string;
}

interface Admin {
    name: string;
    age: number;
    role: string;
}

export type Person = User | Admin;

export const persons: Person[] = [
    {
        name: 'Max Mustermann',
        age: 25,
        occupation: 'Chimney sweep'
    },
    {
        name: 'Jane Doe',
        age: 32,
        role: 'Administrator'
    },
    {
        name: 'Kate Müller',
        age: 23,
        occupation: 'Astronaut'
    },
    {
        name: 'Bruce Willis',
        age: 64,
        role: 'World saver'
    }
];

export function logPerson(person: Person) {
    let additionalInformation: string;
    if (person.role) {
        additionalInformation = person.role;
    } else {
        additionalInformation = person.occupation;
    }
    console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
}

persons.forEach(logPerson);

타입가드를 활용하여 logPerson 함수의 타입에러를 수정해야 한다.

interface User {
    name: string;
    age: number;
    occupation: string;
}

interface Admin {
    name: string;
    age: number;
    role: string;
}

export type Person = User | Admin;

export const persons: Person[] = [
    {
        name: 'Max Mustermann',
        age: 25,
        occupation: 'Chimney sweep'
    },
    {
        name: 'Jane Doe',
        age: 32,
        role: 'Administrator'
    },
    {
        name: 'Kate Müller',
        age: 23,
        occupation: 'Astronaut'
    },
    {
        name: 'Bruce Willis',
        age: 64,
        role: 'World saver'
    }
];

export function logPerson(person: Person) {
    let additionalInformation: string;
    if ("role" in person) {
        additionalInformation = person.role;
    } else {
        additionalInformation = person.occupation;
    }
    console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
}

persons.forEach(logPerson);​

in 연산자를 활용해서 해결하기.

interface User {
    name: string;
    age: number;
    occupation: string;
}

interface Admin {
    name: string;
    age: number;
    role: string;
}

export type Person = User | Admin;

export const persons: Person[] = [
    {
        name: 'Max Mustermann',
        age: 25,
        occupation: 'Chimney sweep'
    },
    {
        name: 'Jane Doe',
        age: 32,
        role: 'Administrator'
    },
    {
        name: 'Kate Müller',
        age: 23,
        occupation: 'Astronaut'
    },
    {
        name: 'Bruce Willis',
        age: 64,
        role: 'World saver'
    }
];

export function isAdmin(person: Person): person is Admin{
    return 'role' in person
}

export function logPerson(person: Person) {
    let additionalInformation: string;
    if (isAdmin(person)) {
        additionalInformation = person.role;
    } else {
        additionalInformation = person.occupation;
    }
    console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
}

persons.forEach(logPerson);​

사용자 정의 타입가드를 활용할 수도 있다.