Swift dictionary with weak references simple example

WeakBox.swift

struct WeakBox<ItemType: AnyObject> {
    weak var item: ItemType?

    init(item: ItemType?) {
        self.item = item
    }
}

WeakBoxExampleTests.swift

//
//  WeakBox.swift
//  Injectable
//
//  Created by Nicholas Cross on 9/2/19.
//  Copyright © 2019 Nicholas Cross. All rights reserved.
//

import XCTest

class WeakBoxExampleTests: XCTestCase {

    func testWeakDictionary() {
        var weakDictionary: [String: WeakBox<Example>] = [:]

        var example: Example? =  Example()
        weakDictionary["example"] = WeakBox(item:example)

        XCTAssertNotNil(weakDictionary["example"]?.item)
        example = nil
        XCTAssertNil(weakDictionary["example"]?.item)
    }

}

Xample.swift

class Example {

}