> Hi! Why there are "super visit*: anObject" in some visit* methods
> of PRWikiWriter? For example #visitHeader and #visitListItem. But
> some methods doesn't use "super visit*: anObject". Where is a
> difference of this need to use "super visit*: anObject" or not?
It is probably the easiest if you put a #halt somewhere and stop
trough the code, then you see what actually happens.
To explain it in words: you are walking over the wiki document AST.
It has leaf (PRText, PRAnchor, PRHorizontalRule, ...) and non-leaf
nodes (PRParagraph, PRTableCell, PRFormat, ...). All the non-leaf
nodes are subclasses of PRDocumentGroup that defines the logic for
child-elements.
Now in the visitor, if you have for example a look at
PRWikiWriter>>visitHorizontalRule: anObject
self newLine; nextPutAll: anObject class markup
With PRParagraph this looks different:
PRWikiWriter>>visitParagraph: anObject
self newLine.
super visitParagraph: anObject
If you have a look at the super implementation you see it delegates
(along its hierarchy) to
PRVisitor>>visitParagraph: anObject
self visitDocumentGroup: anObject
and finally to
PRVisitor>>visitDocumentGroup: anObject
self visitAll: anObject children
So it is used to get the default behavior of the superclass, what is
"visit my children" in this case.
All visitors basically delegate along their hierarchy to get default
behavior. In rare cases I use shortcuts (for example the search), to
avoid walking trough the whole model.
So, not implementing means default behavior. Calling super means
added behavior + default behavior.
Does that make sense?
Lukas
--
Lukas Renggli
http://www.lukas-renggli.ch_______________________________________________
SmallWiki, Magritte, Pier and Related Tools ...
https://www.iam.unibe.ch/mailman/listinfo/smallwiki
Locked
