ViewModel, binding and generic

DynamicBinding.swift

// Ispired by http://rasic.info/bindings-generics-swift-and-mvvm/
class Dynamic<T> {
    typealias Listener = (T) -> Void
    var listener: Listener?
    
    func bind(listener: Listener?) {
        self.listener = listener
    }
    
    func bindAndFire(listener: Listener?) {
        self.listener = listener
        listener?(value)
    }
    
    var value: T {
        didSet {
            listener?(value)
        }
    }
    
    init(_ varible: T) {
        value = varible
    }
}

// Unit test

    func testDynamicInt() {
        let sut = Dynamic(3)
        
        XCTAssertEqual(sut.value, 3) // ✅
        
        sut.bindAndFire { (value) in
            XCTAssertEqual(value, 3) // ✅
        }
    }

    func testDynamicString() {
        let sut = Dynamic("test_1")
        
        XCTAssertEqual(sut.value, "test_1") // ✅
        
        sut.bind { (value) in
            XCTAssertEqual(value, "t") // ❌
        }
    }

LoginViewModel.swift

import Foundation
import RxSwift

protocol GenericViewModel {
    associatedtype T
    
    var generic: T { get set }
    
    func getValue() -> T
}

struct LoginViewModel: GenericViewModel {
    typealias T = String
    
    var generic: T {
        didSet {
            self.username.value = generic
        }
    }
    
    private let username = Variable<T>("")
    
    init(username: String) {
        self.generic = username
    }
    
    func getValue() -> String {
        return username.value
    }
    
    /// Temporary func to test Generic impelementation
    ///
    /// - Returns: The username String
    func getUsername() -> String {
        return username.value
    }
}

// Unit Test
    func testConstructur() {
        var sut: LoginViewModel = LoginViewModel(username: "test_1")
        
        XCTAssertEqual(sut.getUsername(), "test_1") // ❌
        XCTAssertEqual(sut.generic, "test_1") // ✅
        
        sut.generic = "test_2"
        XCTAssertEqual(sut.getUsername(), "test_2") // ✅
        XCTAssertEqual(sut.getValue(), "test_2") // ✅
    }