[Twisted-Python] Deferred getChild (#3621)

[Maarten ter Huurne]

On Monday 30 May 2011, Laurens Van Houtven wrote:

> My use case for this is txYoga <https://github.com/lvh/txyoga>. Long
> story short, it lets you write REST-y webapps. So, you could have
> something like:
> 
> http://www.twistedmatrix.com/labs/glyph
> 
> In local jargon, labs is a collection, and glyph is an element in it.
> Right now, the only collection that actually exists is an in-memory one,
> and the next one I'm going to write is a SQLite one, so blocking on
> child access seems relatively reasonable. In general, however, this
> should be implemented using Deferreds, since the information about glyph
> might be stored in a database far, far away.

A possible alternative would be to create a child resource that remembers 
the child name and do the database lookup in the render method. If there is 
a matching record, render a page with its data, otherwise render a 404 page.

I cannot predict whether the resulting code would be clean or ugly though, 
so I don't know how feasible this approach is.

Bye,
		Maarten