"Globally caching a thread-unsafe class instance" for thread-safe class

[Former user]

I am getting the above mentioned warning for storing instances of NSDateFormatter in a static variable although since iOS 7 NSDateFormatter is thread-safe. See NSDateFormatter Class Reference

[Ali Rantakari]

Thanks for reporting this. Diagnostics for NSDateFormatter can be suppressed by removing it from the default value of the classNames option for this rule. I will consider automatically whitelisting this in certain cases (e.g. if the minimum deployment target is iOS 7+ — the situation on OS X is a bit more complicated, and whitelisting might not be such a good idea there.)

[Ali Rantakari]

In the next version, these diagnostics will be suppressed for NSDateFormatter and NSNumberFormatter if the minimum deployment target is at least iOS 7.