[squeak-dev] Re: [ANN] CoroutineReadStream (again)

Colin Putney cputney at wiresong.ca
Tue Dec 15 00:30:18 UTC 2009

On 2009-12-14, at 12:10 PM, Stephen Pair wrote:

> Can you describe how it would be used with Filesystem?

Filesystem makes use of a Guides and Visitors pattern for traversing directory trees. The guides drive execution, walking around the filesystem in a specific order, and sending #visitDirectory: and #visitFile: to their visitor. You implement directory-tree operations by implementing a subclass of FSVisitor. 

That all works fine, but I'd like to provide a bit of flexibility in the interface. The idea was to provide a CoroutineVisitor that would transform the visiting callbacks into a ReadStream interface. Then you could do something like this:

stream := FSBreathFirstGuide readStreamOn: aReference.

Now, the guides that Filesystem provides are written in such a way that it wouldn't be too hard to invert control and provide a stream interface without coroutines. But I want it to be easy for client applications to implement guides, and not being able to keep state on the activation stack would make things difficult. 


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