在Swift中使用UI_USER_INTERFACE_IDIOM（）检测当前设备

Question

UI_USER_INTERFACE_IDIOM()在iPhone和iPad之间检测到的Swift 相当于什么？

Use of unresolved identifier在Swift中编译时出现错误。

Answer 1

使用Swift时，您可以使用enum UIUserInterfaceIdiom，定义为：enum UIUserInterfaceIdiom : Int {    case unspecified    case phone // iPhone and iPod touch style UI    case pad // iPad style UI}因此，您可以将其用作：UIDevice.current.userInterfaceIdiom == .padUIDevice.current.userInterfaceIdiom == .phoneUIDevice.current.userInterfaceIdiom == .unspecified或使用Switch语句：    switch UIDevice.current.userInterfaceIdiom {    case .phone:        // It's an iPhone    case .pad:        // It's an iPad    case .unspecified:        // Uh, oh! What could it be?    }UI_USER_INTERFACE_IDIOM() 是一个Objective-C宏，定义为：#define UI_USER_INTERFACE_IDIOM() \ ([[UIDevice currentDevice] respondsToSelector:@selector(userInterfaceIdiom)] ? \ [[UIDevice currentDevice] userInterfaceIdiom] : \ UIUserInterfaceIdiomPhone)另外，请注意，即使在使用Objective-C时，UI_USER_INTERFACE_IDIOM()也仅在定位iOS 3.2及更低版本时才需要该宏。部署到iOS 3.2及更高版本时，可以[UIDevice userInterfaceIdiom]直接使用。

Answer 2

Swift 2.0和iOS 9和Xcode 7.1// 1. request an UITraitCollection instancelet deviceIdiom = UIScreen.mainScreen().traitCollection.userInterfaceIdiom// 2. check the idiomswitch (deviceIdiom) {case .Pad:    print("iPad style UI")case .Phone:    print("iPhone and iPod touch style UI")case .TV:     print("tvOS style UI")default:    print("Unspecified UI idiom")}Swift 3.0和Swift 4.0// 1. request an UITraitCollection instancelet deviceIdiom = UIScreen.main.traitCollection.userInterfaceIdiom// 2. check the idiomswitch (deviceIdiom) {case .pad:    print("iPad style UI")case .phone:    print("iPhone and iPod touch style UI")case .tv:     print("tvOS style UI")default:    print("Unspecified UI idiom")}使用UITraitCollection。通过UITraitEnvironment协议的traitCollection属性公开了iOS trait环境。以下类别采用了此协议：UIScreenUIWindowUIViewControllerUIPresentationControllerUIView