Implementing a Reactive Set in Vue.js with TypeScript

Vue.js offers powerful reactivity systems for managing state. While arrays and objects are well-supported, implementing a reactive Set directly requires a custom approach. This challenge will guide you through creating a reactive Set that seamlessly integrates with Vue's reactivity system, allowing for automatic UI updates when the Set's content changes.

Problem Description

Your task is to create a custom composable function in Vue.js (using TypeScript) that mimics the behavior of a native Set but is fully reactive. This means that any changes to the Set (adding, deleting, clearing elements) should automatically trigger re-renders in Vue components that use it.

Key Requirements:

1. Reactive State: The Set's internal data must be observable by Vue.
2. Set API Mimicry: The composable should expose methods that mirror the standard Set API, such as add, delete, has, clear, and a way to iterate over elements (e.g., through a computed property or by returning the underlying data structure).
3. Type Safety: Utilize TypeScript for robust type checking.
4. Composable Function: The solution should be encapsulated within a composable function (e.g., useReactiveSet).

Expected Behavior:

• When an element is added to the reactive Set, any component displaying the Set's contents should update to reflect the new element.
• When an element is deleted, the UI should update accordingly.
• When the Set is cleared, the UI should reflect an empty Set.
• The has method should correctly report the presence of an element.

Edge Cases:

• Handling different data types within the Set (primitives, objects).
• Ensuring correct reactivity when deleting an element that is not present.
• Initializing the reactive Set with existing values.

Examples

Example 1: Basic Usage

// In your Vue component:
import { useReactiveSet } from './useReactiveSet';
import { computed } from 'vue';

const mySet = useReactiveSet<string>(['apple', 'banana']);

const itemCount = computed(() => mySet.size); // mySet.size will be 2

// Adding an element
mySet.add('orange');
// itemCount should now be 3

// Deleting an element
mySet.delete('banana');
// itemCount should now be 2

// Checking for an element
const hasApple = mySet.has('apple'); // true
const hasBanana = mySet.has('banana'); // false

// Clearing the set
mySet.clear();
// itemCount should now be 0

Output (for the component using itemCount): Initially: 2 After add('orange'): 3 After delete('banana'): 2 After clear(): 0

Explanation: The useReactiveSet composable allows us to create a Set that Vue's reactivity system tracks. Changes to the Set (like adding or deleting elements) automatically update computed properties that depend on its size or content.

Example 2: Reactivity with Objects

interface User {
  id: number;
  name: string;
}

const user1: User = { id: 1, name: 'Alice' };
const user2: User = { id: 2, name: 'Bob' };

const userSet = useReactiveSet<User>([user1, user2]);

// When you add a new user object
const user3: User = { id: 3, name: 'Charlie' };
userSet.add(user3);

// When you delete an existing user object
userSet.delete(user1);

// The computed property will update automatically
const userNameList = computed(() => Array.from(userSet.values()).map(user => user.name));

Output (for userNameList): Initially: ['Alice', 'Bob'] After add(user3): ['Alice', 'Bob', 'Charlie'] After delete(user1): ['Bob', 'Charlie']

Explanation: The reactive Set correctly handles object references. Adding and deleting objects by reference works as expected, triggering reactivity.

Constraints

• The solution must be written in TypeScript.
• The composable function should be named useReactiveSet.
• The solution should not rely on external libraries that specifically provide reactive Sets, but should leverage Vue's built-in reactivity primitives (like ref or reactive).
• The implementation should be efficient enough for typical frontend use cases.

Notes

• Consider how you will expose the underlying Set data or its elements to the Vue template for rendering. A computed property returning Array.from(theSet.values()) is a common approach.
• Think about how to manage the reactivity of the Set's internal data structure itself.
• You'll need to decide whether your useReactiveSet function will return a proxy, a ref, or a custom object with reactive properties.