typescript-exercises（六）

请热爱劳动，即使不是靠它吃饭，也可以为了身体的缘故而爱它，它可以增进身心健康，免除怠惰之累。——潘恩

题目：

/*

Intro:

    Filtering requirements have grown. We need to be
    able to filter any kind of Persons.

Exercise:

    Fix typing for the filterPersons so that it can filter users
    and return User[] when personType='user' and return Admin[]
    when personType='admin'. Also filterPersons should accept
    partial User/Admin type according to the personType.
    `criteria` argument should behave according to the
    `personType` argument value. `type` field is not allowed in
    the `criteria` field.

Higher difficulty bonus exercise:

    Implement a function `getObjectKeys()` which returns more
    convenient result for any argument given, so that you don't
    need to cast it.

    let criteriaKeys = Object.keys(criteria) as (keyof User)[];
    -->
    let criteriaKeys = getObjectKeys(criteria);

*/

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 logPerson(person: Person) {
    console.log(
        ` - ${person.name}, ${person.age}, ${person.type === 'admin' ? person.role : person.occupation}`
    );
}

export function filterPersons(persons: Person[], personType: string, criteria: unknown): unknown[] {
    return persons
        .filter((person) => person.type === personType)
        .filter((person) => {
            let criteriaKeys = Object.keys(criteria) as (keyof Person)[];
            return criteriaKeys.every((fieldName) => {
                return person[fieldName] === criteria[fieldName];
            });
        });
}

export const usersOfAge23 = filterPersons(persons, 'user', { age: 23 });
export const adminsOfAge23 = filterPersons(persons, 'admin', { age: 23 });

console.log('Users of age 23:');
usersOfAge23.forEach(logPerson);

console.log();

console.log('Admins of age 23:');
adminsOfAge23.forEach(logPerson);

// In case you are stuck:
// https://www.typescriptlang.org/docs/handbook/2/functions.html#function-overloads

报错：

index.ts(65,44): error TS2769: No overload matches this call.
  Overload 1 of 2, '(o: {}): string[]', gave the following error.
    Argument of type 'unknown' is not assignable to parameter of type '{}'.
  Overload 2 of 2, '(o: object): string[]', gave the following error.
    Argument of type 'unknown' is not assignable to parameter of type 'object'.
index.ts(67,46): error TS2571: Object is of type 'unknown'.
index.ts(76,22): error TS2345: Argument of type '(person: Person) => void' is not assignable to parameter of type '(value: unknown, index: number, array: unknown[]) => void'.
  Types of parameters 'person' and 'value' are incompatible.
    Type 'unknown' is not assignable to type 'Person'.
      Type 'unknown' is not assignable to type 'Admin'.
index.ts(81,23): error TS2345: Argument of type '(person: Person) => void' is not assignable to parameter of type '(value: unknown, index: number, array: unknown[]) => void'.
test.ts(13,5): error TS2344: Type 'false' does not satisfy the constraint 'true'.
test.ts(21,5): error TS2344: Type 'false' does not satisfy the constraint 'true'.
test.ts(29,5): error TS2344: Type 'false' does not satisfy the constraint 'true'.
test.ts(37,5): error TS2344: Type 'false' does not satisfy the constraint 'true'.

答案：

/*

Intro:

    Filtering requirements have grown. We need to be
    able to filter any kind of Persons.

Exercise:

    Fix typing for the filterPersons so that it can filter users
    and return User[] when personType='user' and return Admin[]
    when personType='admin'. Also filterPersons should accept
    partial User/Admin type according to the personType.
    `criteria` argument should behave according to the
    `personType` argument value. `type` field is not allowed in
    the `criteria` field.

Higher difficulty bonus exercise:

    Implement a function `getObjectKeys()` which returns more
    convenient result for any argument given, so that you don't
    need to cast it.

    let criteriaKeys = Object.keys(criteria) as (keyof User)[];
    -->
    let criteriaKeys = getObjectKeys(criteria);

*/

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 logPerson(person: Person) {
    console.log(
        ` - ${person.name}, ${person.age}, ${person.type === 'admin' ? person.role : person.occupation}`
    );
}

export function getObjectKeys<T>(obj:T){
    return Object.keys(obj) as (keyof T)[]
}

export function filterPersons(persons: Person[], personType: User['type'], criteria: Partial<Omit<User,'type'>>):User[];
export function filterPersons(persons: Person[], personType: Admin['type'], criteria: Partial<Omit<Admin,'type'>>):Admin[];
export function filterPersons(persons: Person[], personType: Person['type'], criteria: Partial<Person>):Person[]{
    return persons
        .filter((person) => person.type === personType)
        .filter((person) => {
            let criteriaKeys = getObjectKeys(criteria);
            return criteriaKeys.every((fieldName) => {
                return person[fieldName] === criteria[fieldName];
            });
        });
}

export const usersOfAge23 = filterPersons(persons, 'user', { age: 23 });
export const adminsOfAge23 = filterPersons(persons, 'admin', { age: 23 });

console.log('Users of age 23:');
usersOfAge23.forEach(logPerson);

console.log();

console.log('Admins of age 23:');
adminsOfAge23.forEach(logPerson);

// In case you are stuck:
// https://www.typescriptlang.org/docs/handbook/2/functions.html#function-overloads

主要是考察方法重载和范型使用