iPhone设备
物理分辨率是硬件所支持的，逻辑分辨率是软件可以达到的。
如图所示：
iPhone5和6的比例是不变的。
iPod设备
iPad设备
所有设备型号官网地址：https://www.theiphonewiki.com/wiki/Models
//获得屏幕的宽高
#define kScreenWidth ([UIScreen mainScreen].bounds.size.width)
#define kScreenHeight ([UIScreen mainScreen].bounds.size.height)
//iPhoneX / iPhoneXS
#define isIphoneX_XS (kScreenWidth == 375.f && kScreenHeight == 812.f ? YES : NO)
//iPhoneXR / iPhoneXSMax
#define isIphoneXR_XSMax (kScreenWidth == 414.f && kScreenHeight == 896.f ? YES : NO)
//异性全面屏
#define isFullScreen (isIphoneX_XS || isIphoneXR_XSMax)
// Status bar height.
#define StatusBarHeight (isFullScreen ? 44.f : 20.f)
// Navigation bar height.
#define NavigationBarHeight 44.f
// Tabbar height.
#define TabbarHeight (isFullScreen ? (49.f+34.f) : 49.f)
// Tabbar safe bottom margin.
#define TabbarSafeBottomMargin (isFullScreen ? 34.f : 0.f)
// Status bar & navigation bar height.
#define StatusBarAndNavigationBarHeight (isFullScreen ? 88.f : 64.f)