Description
Allow adding new behaviors to existing class hierarchy without altering existing code.
This pattern is particularly useful when, you cannot modify existing classes but need to add new features.
Example
| User.cs
|
public class User : IUser
{
public string Name { get; set; }
public User(string name)
{
this.Name = name;
}
public void Accept(IVisitor visitor)
{
visitor.Visit(this);
}
}
|
| IVisitor.cs
|
public interface IVisitor
{
void Visit(User user);
}
|
| TitleVisitor.cs
|
public class TitleVisitor : IVisitor
{
public string Title { get; set; }
public TitleVisitor(string title)
{
this.Title = title;
}
public void Visit(Employee employee)
{
employee.Name += $" ({this.Title})";
}
}
|
|
var user = new User("Nicolas");
Console.WriteLine(user.Name); // Nicolas
user.Accept(new TitleVisitor("Boss"));
Console.WriteLine(user.Name); // Nicolas (Big Boss)
|
