On Tue, Dec 31, 2002 at 12:47:24AM -0500, Christopher Armstrong wrote:
The one other place where I thought this might be useful is in IRCClient. IRC commands often result in several messages in response -- something like list, or whois, for example. If we wanted to abstract this interface, we could have a "list" method that returned a Deferred that didn't trigger until *all* the list lines have been received.
Actually, I just realised, I fibbed about FTPClient... it does something a little unusual, and I'm interested in opinions on this. Say you call FTPClient.list(). You don't get a Deferred, you actually have to pass in a Protocol *instance*, and as the data for FTPClient.list is received, it gets passed straight to that Protocol, via dataReceived. In fact, the FTPClient internally makes a Factory for that connection, which (essentially) uses that Protocol, but that's an implementation detail. This is a bit weird, though, because using an FTPClient involves creating Protocols without associated Factories, and nowhere else in Twisted does that. [The reason why I got confused about Deferreds in the interface, is that I use Deferreds internally in FTPClient to manage all this.] So this is actually another interface, possibly specific to FTP, where you pass a Protocol instance -- this allows for progressive processing of data, rather than all-at-once, and this feels "more Twisted" to me :) So, to parse the results of an FTP listing, you pass in a FTPFileListProtocol... this is useful, but there probably should be a higher-level interface to this that returns a Deferred, for when you don't need to do custom parsing and don't care about progressive processing (i.e. most of the time).
So, as an _implementation_ strategy, the "handle_FOO" methods are great when the mapping of message-level request to message-level response is 1:many, and for interfaces, Deferreds are great.
Agreed. In FTP, there is, basically, only one response per request, so I don't have need for handle_FOO in the FTPClient. In POP3, I think the situation is similar (but simpler than FTP). For IRC, handle_FOO makes good sense. -Andrew.