Question

Background: During the handshake process, my iOS app learns the server capabilities by

1. Checking its header information in didReceiveResponse

   AND

2. Parsing its response XML in connectionDidFinishLoading

Problem statement: Since callback #1 precedes #2, I am storing the version string in didReceiveResponse and checking it later in connectionDidFinishLoading when the response is available.

This fortunately works fine so far because #1 preceeds #2. But is that order always guaranteed by network / iOS?

Answer 1

According to the documentation:

Zero or more connection:didReceiveResponse: messages will be sent to the delegate before receiving a connection:didReceiveData: message. The only case where connection:didReceiveResponse: is not sent to a delegate is when the protocol implementation encounters an error before a response could be created.
Zero or more connection:didReceiveData: messages will be sent before any of the following messages are sent to the delegate: connection:willCacheResponse:, connectionDidFinishLoading:, connection:didFailWithError:.

So unless there’s an error, you can guarantee that you’ll get a didReceiveResponse before getting a connectionDidFinishLoading.