Check for class existence in Swift

Question

I want to use NSURLQueryItem in my Swift iOS app. However, that class is only available since iOS 8, but my app should also run on iOS 7. How would I check for class existence i

Answer 1

Swift 2.0 provides us with a simple and natural way to do this.It is called API Availability Checking.Because NSURLQueryItem class is only available since iOS8.0,you can do in this style to check it at runtime.

    if #available(iOS 8.0, *) {
        // NSURLQueryItem is available

    } else {
        // Fallback on earlier versions
    }

Answer 2

Try this:

if objc_getClass("NSURLQueryItem") != nil {
   // iOS 8 
} else {
   // iOS 7
}

I've also done it like this too:

if let theClass: AnyClass = NSClassFromString("NSURLQueryItem") {
    // iOS 8
} else {
    // iOS 7
}

Or, you can also check system version like so, but this isn't the best practice for iOS dev - really you should check if a feature exists. But I've used this for a few iOS 7 hacks... pragmatism over purity.

    switch UIDevice.currentDevice().systemVersion.compare("8.0.0", options: NSStringCompareOptions.NumericSearch) {
    case .OrderedSame, .OrderedDescending:
        iOS7 = false
    case .OrderedAscending:
        iOS7 = true
    }

Answer 3

Simplest way I know of

if NSClassFromString("NSURLQueryItem") != nil {
    println("NSURLQueryItem exists")
}else{
    println("NSURLQueryItem does not exists")
}