Adam Sampson's threading bookmarkshttps://bookmarks.offog.org/ats/threadingAdam Sampson2014-07-26T15:05:42Zmikeash.com: Friday Q&A 2014-06-06: Secrets of dispatch_oncehttps://bookmarks.offog.org/edit?url=https%3A%2F%2Fmikeash.com%2Fpyblog%2Ffriday-qa-2014-06-06-secrets-of-dispatch_once.html2014-07-26T15:05:42ZNice worked example of how to implement dispatch_once.