If you’re developing apps for iOS then you should be (painfully) familiar with the Key-Value Observing (KVO) pattern. Says Chief NSHipster Matt Thompson about KVO:
Ask anyone who’s been around the NSBlock a few times: Key-Value Observing has the worst API in all of Cocoa. It’s awkward, verbose, and confusing. And worst of all, its terrible API belies one of the most compelling features of the framework.
Unfortunately, KVO seems to be the best way to natively achieve data binding on the iOS platform.