As an iOS developer, it’s important to know the version of the operating system (OS) that your app is running on. This information can help you optimize your app for the specific features and capabilities of that OS, as well as ensure that your app is compatible with a wide range of devices and users.

Using System Information

One of the most straightforward ways to determine the iOS version that your app is running on is to use system information. This can be accessed through the NSUserDefaults class in Xcode, or by using the UIApplication class in Swift.

In Xcode, you can access system information by adding the following code to your view controller’s viewDidLoad() method:

swift
if let systemInfo = NSUserDefaults.standard.object(forKey: "systemVersion") as? String {
print("iOS version: (systemInfo)")
}

This code will print the iOS version to the console, where you can then inspect it and use it to optimize your app for that specific version.

In Swift, you can access system information by using the UIApplication class and calling its applicationVersion property:

swift
if let version = UIApplication.shared.applicationVersion {
print("iOS version: (version)")
}

This code will also print the iOS version to the console, where you can then inspect it and use it to optimize your app for that specific version.

Using Device Properties

Another way to determine the iOS version that your app is running on is to use device properties. This information can be accessed through the UIDevice class in Xcode, or by using the UIScreen class in Swift.

In Xcode, you can access device properties by adding the following code to your view controller’s viewDidLoad() method:

swift
if let osVersion = UIDevice.current.systemVersion.major as? Int {
print("iOS version: (osVersion)")
}

This code will print the major version of the iOS operating system to the console, where you can then inspect it and use it to optimize your app for that specific version.

In Swift, you can access device properties by using the UIScreen class and calling its mainScreen. You can then access the device’s properties using the UIDevice class:

swift
if let screen = UIScreen.main.bounds.screen {
if let osVersion = screen.systemVersion.major as? Int {
print("iOS version: (osVersion)")
}
}

This code will also print the major version of the iOS operating system to the console, where you can then inspect it and use it to optimize your app for that specific version.

Using Third-Party Libraries

In addition to using system information and device properties, there are several third-party libraries available that can help you determine the iOS version that your app is running on. These libraries can be especially useful if you need more granular control over how your app behaves on different OSes.

One popular library for this purpose is Podspec in Ruby. This library allows you to define platform-specific dependencies in your app’s .podspec file, and then automatically download and link the appropriate version of the library based on the iOS version that your app is running on.

Another popular library is React Native in JavaScript.