NSError domains / custom domains - conventions and best practices

Question

NSError requires a domain, which I understand segments the range of error codes.

One would anticipate that there exist somewhere a registry of domain.error code but

Answer 1

Apple generally publishes their NS/CFError codes in a header named FrameworkNameErrors.h. For example, Foundation's error codes are in Foundation/FoundationErrors.h. In addition, they generally publish the domain and codes in their documentation for the framework.

Any independent author of a framework with its own error domain and codes should do the same.