First, you have to ask permission from the user to use their IDFA:
#import <AppTrackingTransparency/AppTrackingTransparency.h>
[ATTrackingManager requestTrackingAuthorizationWithCompletionHandler:^(ATTrackingManagerAuthorizationStatus status) {
// Tracking authorization completed. Start loading ads here.
}];
This permission flow will only run once, the first time it is called, even if you re-start the app and/or call it again. If you want to answer differently, you’ll have to delete the app off the device or simulator completely and reinstall it. Note that iOS simulators return blanked IDFAs (all zeroes) no matter what the answer to the permission flow. See https://developer.apple.com/documentation/apptrackingtransparency for details, including how to customize the message shown to users when asking to track them. Note that many advertising SDKs have their own consent flow calls that you can use.
To actually get the IDFA once you have permission:
#import <AdSupport/ASIdentifierManager.h>
If you would like to get it as an NSString, use:
[[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString]
So your code might look like this:
NSString *idfaString = [[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString];
NSLog (@"IDFA: %@", idfaString);