ViewModel.swift

import Foundation
import Bond

class ViewModel {
    let name = Observable<String?>(nil)
    let greeting = Observable<String?>(nil)
    lazy var sayHelloCommand: ActionCommand = {
        return ActionCommand { [unowned self] in
            self.sayHello()
        }
    }()
    
    private func sayHello() {
        greeting.value = "Hello, \(name.value ?? "")"
    }
}