Why must the caller retain the new object for JKArray methods about jsonkit HOT 1 CLOSED

Some of this is covered in CHANGELOG.md, but the short explanation is that this implements a "transfer of ownership" memory management policy.

The normal object ownership flow for collections usually has the collection CFRetain an object when it is added to the collection via a AddToCollection type of call. Once added to the collection, whatever added it to the collection must call CFRelease in order to balance things out.

With a "transfer of ownership" type of policy, the collection omits the CFRetain, and the whatever is adding the object to the collection omits the CFRelease. The retain counts balance out to be the same, with two fewer retain / release calls.

Since the number of objects that JSONKit creates tends to be a lot, eliminating these calls actually improves performance. Part of the reason why it results in a performance increase is because the retain and release calls (for the types of objects JSONKit creates) are implemented with atomic CPU primitives, which have a tendency to be "very expensive" to execute.

from jsonkit.