B/O - Memento

• Category: behavioral
• Type: object
• Motivation: memento is capture and storing the current state of an object in a manner that it can be restored later on in a smooth manner

// caretaker
do {
    var history: [Memento] = []

    let editor = Editor()
    editor.type("foo")
    history.append(editor.save())
    print(editor.content)

    editor.type("bar")
    print(editor.content)

    editor.restore(history[0])
    print(editor.content)
}

// memento
struct Memento
{
    let content: String
}

// originator
class Editor
{
    var content: String = ""
    func type(_ words: String)
    {
        content += words
    }

    func save() -> Memento
    {
        return Memento(content: content)
    }

    func restore(_ memento: Memento)
    {
        content = memento.content
    }
}