if(UI_USER_INTERFACE_IDIOM () == UIUserInterfaceIdiom.pad)
 {
            print("This is iPad")
 }else if (UI_USER_INTERFACE_IDIOM () == UIUserInterfaceIdiom.phone)
 {
            print("This is iPhone");
  }

你也可以用这个

#define IPAD UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad
...
if (IPAD) {
   // iPad
} else {
   // iPhone / iPod Touch
}

这是iOS 3.2的UIDevice的一部分，例如:

[UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad

在Swift 4.2和Xcode 10中

if UIDevice().userInterfaceIdiom == .phone {
    //This is iPhone
} else if UIDevice().userInterfaceIdiom == .pad { 
    //This is iPad
} else if UIDevice().userInterfaceIdiom == .tv {
    //This is Apple TV
}

如果你想检测特定的设备

let screenHeight = UIScreen.main.bounds.size.height
if UIDevice().userInterfaceIdiom == .phone {
    if (screenHeight >= 667) {
        print("iPhone 6 and later")
    } else if (screenHeight == 568) {
        print("SE, 5C, 5S")
    } else if(screenHeight<=480){
        print("4S")
    }
} else if UIDevice().userInterfaceIdiom == .pad { 
    //This is iPad
}

if(UI_USER_INTERFACE_IDIOM () == UIUserInterfaceIdiom.pad)
 {
            print("This is iPad")
 }else if (UI_USER_INTERFACE_IDIOM () == UIUserInterfaceIdiom.phone)
 {
            print("This is iPhone");
  }

*

在swift 3.0中

*

 if UIDevice.current.userInterfaceIdiom == .pad {
        //pad
    } else if UIDevice.current.userInterfaceIdiom == .phone {
        //phone
    } else if UIDevice.current.userInterfaceIdiom == .tv {
        //tv
    } else if UIDevice.current.userInterfaceIdiom == .carPlay {
        //CarDisplay
    } else {
        //unspecified
    }