If I have a bundle identifier as a String, how do I find out the URL of the bundle that it identifies? Conversely, if I have the URL of a bundle, how do I find out that bundle's identifier as a String?
I would like to only use Foundation/Cocoa APIs to do this.
You can use Bundle's init(identifier:) followed by bundleURL to get a URL from a bundle identifier, and Bundle's init(url:) followed by bundleIdentifier to get a bundle's URL.
let myBundleUrl = Bundle(identifier: "com.me.app")?.bundleURL
let theirBundleId = Bundle(url: URL(fileURLWithPath: "/Applications/Mail.app"))?.bundleIdentifier
Just as a note, NSWorkspace also has an API for getting a URL from a given bundle ID: urlForApplication(withBundleIdentifier:). I didn't recommend this one here because NSWorkspace doesn't have an API for getting an identifier from a URL.