static void Main(string[] args)
{
/*
* More info: https://manski.net/2013/05/the-visitor-pattern-explained
* What problems can the Visitor design pattern solve?
*
* It should be possible to define a new operation for (some) classe
* s of an object structure without changing the classes.
*
* When new operations are needed frequently and the object structure consists of many unrelated classes,
* it's inflexible to add new subclasses each time a new operation is required because "[..] distributing
* all these operations across the various node classes leads to a system that's hard to understand, maintain, and change."
*
*/
var doc = new Document(new PlainText {
Text = "Plain"
}, new Hyperlink {
Text = "Hyper", Url = "Link"
});
var visitor = new HtmlVisitor();
doc.Accept(visitor);
Console.WriteLine($"Plain text plus Hyperlink {visitor.Output}");
var doc2 = new Document(new PlainText {
Text = "Plain"
}, new Hyperlink {
Text = "Hyper", Url = "Link"
});
var visitor2 = new LatexVisitor();
doc.Accept(visitor);
Console.WriteLine($"Plain text plus Hyperlink {visitor.Output}");
}
public void TestVisitor()
{
var document = new Document();
document.AddPart(new BoldText("This is bold text."));
document.AddPart(new PlainText("This is plain text."));
document.AddPart(new Hyperlink("This is hyperlink.", "http://www.example.com"));
var htmlVisitor = new HtmlVisitor();
document.Accept(htmlVisitor);
Assert.That(
htmlVisitor.Output,
Is.EqualTo("<b>This is bold text.</b>This is plain text.<a href=\"http://www.example.com\">This is hyperlink.</a>"));
var latexVisitor = new LatexVisitor();
document.Accept(latexVisitor);
Assert.That(
latexVisitor.Output,
Is.EqualTo("\\textbf{This is bold text.}This is plain text.\\href{http://www.example.com}{This is hyperlink.}"));
}
public static string ToLaTeX(this DocumentPart part)
{
Visitor visitor = new LatexVisitor();
return(visitor.Visit(part));
}
