Simply like website development there has been rapid growth and a steady requirement for quality motivation in iOS app designs. At times it might be difficult to develop an iOS app. But if you hire iPhone app developer with good experience you end up on a good note.
Apple has been in a versatile world for quite a long time with its iPhone and iPad arrangement. In spite of the price increase it makes with each official release, it has eventually only increased its number of users and popularity, and this is presumably the reason that most customers will need their application to existing on the app store; in turn making it a necessity for the mobile app developers to learn the designing & development of iOS applications.
Luckily, Apple is out with its worth wait update which has free Apple UI design resources for Apple mobiles, tvOS apps design resources & watchOS apps design resources.