−using System;
using System.Collections.Generic;
using System.Linq;
var editor = new TextEditor();
editor.Write("draft");
ISnapshot saved = editor.Save();
editor.Write("edited");
Console.WriteLine(editor.Restore(saved));
Console.WriteLine(editor.Text);
interface ISnapshot { }
// Keep interpretation and restoration of saved state inside the original editor.
sealed class TextEditor
{
private readonly Guid id = Guid.NewGuid();
private sealed record Snapshot(Guid Owner, string Text) : ISnapshot;
public string Text { get; private set; } = "";
public void Write(string text) => Text = text;
// Return only a storage token and retain the actual text privately.
public ISnapshot Save() => new Snapshot(id, Text);
public bool Restore(ISnapshot snapshot)
{
if (snapshot is not Snapshot saved || saved.Owner != id) return false;
Text = saved.Text;
return true;
}
}
+using System;
using System.Collections.Generic;
using System.Linq;
var editor = new TextEditor();
editor.Write("draft");
ISnapshot saved = editor.Save();
editor.Write("edited");
Console.WriteLine(editor.Restore(saved));
Console.WriteLine(editor.Text);
interface ISnapshot { }
// Keep interpretation and restoration of saved state inside the original editor.
sealed class TextEditor
{
private readonly Guid id = Guid.NewGuid();
private sealed record Snapshot(Guid Owner, string Text) : ISnapshot
{
// A record's default ToString prints its property values, so hide them.
public override string ToString() => nameof(ISnapshot);
}
public string Text { get; private set; } = "";
public void Write(string text) => Text = text;
// Expose the snapshot through its common interface; the original editor interprets its private representation.
public ISnapshot Save() => new Snapshot(id, Text);
public bool Restore(ISnapshot snapshot)
{
if (snapshot is not Snapshot saved || saved.Owner != id) return false;
Text = saved.Text;
return true;
}
}
