Swift 4.1 implemented SE-0190, which introduced a new targetEnvironment
condition that lets us differentiate between builds that are for physical devices and those that are for a simulated environment.
At this time targetEnvironment
has only one value, simulator
, which will be true if your build is targeting a simulated device such as the iOS Simulator. For example:
#if targetEnvironment(simulator)
// code for the simulator here
#else
// code for real devices here
#endif
This is useful when writing code to deal with functionality the simulator doesn't support, such as capturing photos from a camera or reading the accelerometer.
As an example, let's look at processing a photo from the camera. If we're running on a real device we'll create and configure a UIImagePickerController()
to take photos using the camera, but if we're in the simulator we'll just load a sample image from our app bundle:
import UIKit
class TestViewController: UIViewController, UIImagePickerControllerDelegate {
// a method that does some sort of image processing
func processPhoto(_ img: UIImage) {
// process photo here
}
// a method that loads a photo either using the camera or using a sample
func takePhoto() {
#if targetEnvironment(simulator)
// we're building for the simulator; use the sample photo
if let img = UIImage(named: "sample") {
processPhoto(img)
} else {
fatalError("Sample image failed to load")
}
#else
// we're building for a real device; take an actual photo
let picker = UIImagePickerController()
picker.sourceType = .camera
vc.allowsEditing = true
picker.delegate = self
present(picker, animated: true)
#endif
}
// this is called if the photo was taken successfully
func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
// hide the camera
picker.dismiss(animated: true)
// attempt to retrieve the photo they took
guard let image = info[UIImagePickerControllerEditedImage] as? UIImage else {
// that failed; bail out
return
}
// we have an image, so we can process it
processPhoto(image)
}
}
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