I am working on an iOS app that has a highly asynchronous design. There are circumstances where a single, conceptual "operation" may queue many child blocks that will be both executed asynchronously and receive their responses (calls to remote server) asynchronously. Any one of these child blocks could finish execution in an error state. Should an error occur in any child block, any other child blocks should be cancelled, the error state should be percolated up to the parent, and the parent's error-handling block should be executed.
I am wondering what design patterns and other tips that might be recommended for working within an environment like this?
I am aware of GCD's dispatch_group_async and dispatch_group_wait capabilities. It may be a flaw in this app's design, but I have not had good luck with dispatch_group_async because the group does not seem to be "sticky" to child blocks.
Thanks in advance!