IOS 开发的官方文档链接

下面这些文章都是苹果官方的开发文档，非常有用：

iOS Developer Library

https://developer.apple.com/library/ios/navigation/

总入口，这个毋需多言了

UIKit Framework Reference

https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIKit_Framework/index.html#//apple_ref/doc/uid/TP40006955

UIKit 框架的指南

Auto Layout Guide

https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/AutolayoutPG/index.html#//apple_ref/doc/uid/TP40010853-CH7-SW1

自动化布局的说明

View Controller Programming Guide for iOS

https://developer.apple.com/library/ios/featuredarticles/ViewControllerPGforiPhoneOS/index.html#//apple_ref/doc/uid/TP40007457-CH2-SW1

视图控制器的说明文档

View Controller Catalog for iOS

https://developer.apple.com/library/ios/documentation/WindowsViews/Conceptual/ViewControllerCatalog/Introduction.html#//apple_ref/doc/uid/TP40011313

iOS Human Interface Guidelines 

https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/MobileHIG/LayoutandAppearance.html

iOS 人机界面的编程，在里面说明了 Regular 和 Compact enviorment 的区别（IPad 无论是横屏(horizontally)还是竖屏(vertically)都是Regular width and height, iPhone 6 plus 横屏为 Regular Width and Compact Height, 竖屏为 Compact Width and Regular Height, iPhone 6, 5, 4 横屏为 compact width and regular height, 竖屏为 compact width and compact height）