I'll add a few of my favourites:

- iOS Dev Weekly (https://iosdevweekly.com/)

- Little Bites of Cocoa (https://littlebitesofcocoa.com/)

- objc (https://www.objc.io/)

- NSHipster (http://nshipster.com/)

- NSBlog / Friday Q&A from Mike Ash (https://www.mikeash.com/pyblog/)

- This Week in Swift (https://swiftnews.curated.co/)

- Erica Sadun (http://ericasadun.com/)

- Quality Coding (http://qualitycoding.org/)

- Use Your Loaf (http://useyourloaf.com/)

- Swift Monthly (http://swiftmonthly.com/)

- Cocoa, Objective-C and Swift programming News aggregator (https://twitter.com/cocoadevblogs)