Visitor Pattern can be replaced with Callback functions?

Question

Is there any significant benefit to using either technique? In case there are variations, the Visitor Pattern I mean is this: http://en.wikipedia.org/wiki/Visitor_pattern And below is an example of using a delegate to achieve the same effect (at least I think it is the same) Say there is a collection of nested elements: Schools contain Departments which contain Students Instead of using the Visitor pattern to perform something on each collection item, why not use a simple callback (Action delegate in C#) Say something like this ``` class Department { List Students; } class School { List Departments; VisitStudents(Action<Student> actionDelegate) { foreach(var dep in this.Departments) { foreach(var stu in dep.Students) { actionDelegate(stu); } } } } School A = new School(); ...//populate collections A.Visit((student)=> { ...Do Something with student... }); ``` *EDIT Example with delegate accepting multiple params Say I wanted to pass both the student and department, I could modify the A…

Accepted Answer

The visitor pattern is usually used when there are more than one type of things that are visited. You have only one type (`Student`s), so you don't really need the visitor pattern and can just pass in a delegate instance.

Assume you'd want to visit both `Department`s and `Student`s. Then you visitor would look like this:

```
interface ISchoolVisitor
{
    void Visit(Department department);
    void Visit(Student student);
}
```

Of course, you could also use delegates here as well, but it would be cumbersome to pass in multiple delegate instances -- in particular if you have more than 2 types of visited things.

Visitor Pattern can be replaced with Callback functions?

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