Follow Up: http-streams and Aeson

Posted on June 5, 2013


In my last post there were (at least) a few things that could be done better. I got some great feedback from the smart people on Hacker News so I’ve made a couple changes to the final source.

The biggest issue is that I was completely losing the benefit of streaming by reading the entire response body in and then parsing it. I knew this but as I mentioned I hadn’t yet figured out how to handle it correctly. Fortunately someone else does, and with their suggestions (and a bit more Googling) I figured it out. It could probably still be cleaned up a little but for these purposes it does the trick.

On line 90 there is a new function called parseJSONFromStream. Calling this on the stream from receiveResponse (and adding the type hint for a Result wrapped around a Feed) gives us a similar situation as we had with Maybe Feed, so the main function does essentially the same thing still. With a little more time we could probably make this cleaner in fetchQuakes by giving the handler more to rather than calling it in a lambda.

And speaking of fetchQuakes, using http-streams’ withConnection cleans it up a little bit by automatically handling closing of the connection. It saves a couple lines of code and makes the function less cluttered.

Thanks again for all of the feedback!