Swift Evolution: Actors(github.com)

    // Safe: this operation is the only one that has access to the actor's isolated
    // state right now, and there have not been any suspension points between
    // the place where we checked for sufficient funds and here.
    balance = balance - amount
    
    // Safe: the deposit operation is placed in the `other` actor's mailbox; when
    // that actor retrieves the operation from its mailbox to execute it, the
    // other account's balance will get updated.
    await other.deposit(amount: amount)

    Once upon a time, there was a company called Taligent, which was created by IBM and Apple to develop a set of    
    tools and libraries like Cocoa. About the time Taligent reached the peak of its mindshare, I met one of its 
    engineers at a trade show. I asked him to create a simple application for me: A window would appear with a  
    button, and when the button was clicked, the words "Hello, World!" would appear in a text field. The engineer 
    created a project and started subclassing madly: subclassing the window and the button and the event handler. 
    Then he started generating code: dozens of lines to get the button and the text field onto the window. After 45 
    minutes, I had to leave. The app still did not work. That day, I knew that the company was doomed. A couple of years   
    later,Taligent quietly closed its doors forever.