How to launch my app programmatically, if an other app opens?

Question

I want, that my app opens when (for example) the user opens iTunes. How Can I do this?

Answer 1

If you are talking iOS; you can't.

Answer 2

Have a program always running in the background that is subscribed to NSWorkspace's NSWorkspaceDidLaunchApplicationNotification and have it do its thing when it sees iTunes as the NSWorkspaceApplicationKey object.