Re: [RBMetacode] Need some code design help

[Joe S. <jo...@st...>]

On Mar 14, 2008, at 8:38 AM, Thomas Tempelmann wrote:

> Now I like to add Find & Replace functionality and I am looking for
> suggestions on how to do this best.
>
> To search, I need to iterate over all items. Currently, not every  
> text item
> of interest has its own node in the tree. Instead, as explained  
> above, the
> name/label is a property of any node's base class, and some classes  
> have
> accessor methods for reading and settings source, declaration and  
> notes.
>
> To iterate over these, I'd currently have to iterate over the  
> nodes, then
> add special handling for the special properties. But how would the  
> iterator
> remember where it's at? If I code it so that it uses a callback  
> (delegate)
> function to handle the finding, it would implicitly remember where  
> it's at,
> but what if the callback function decides to alter the tree so that  
> the
> iteration loop is now working on obsolete items?
>
> Therefore, I believe it's better to have a "smarter" iterator that  
> one calls
> from one's own loop, getting the next found item, then process this  
> item,
> then proceed in the loop to get the next item from the iterator.  
> But then,
> the iterator has to know where it's at. See the problem?

If I understand you properly, I think the find/replace functionality  
should be a visitor (see SyntaxVisitor and its subclasses in  
ParserProto for an example).  And to avoid the problem of the tree  
changing while you're traversing it, do it in two stages: first,  
gather a list of all the matches; and second (if the user wants to  
replace all without seeing them first), do the replacements.

HTH,
- Joe