Why is NSBundle bundleIdentifier optional?

Question

Just wondering why NSBundle bundleIdentifier is optional.

Is there a reason it could be nil?

Answer 1

If you're just building an executable, running a script, or using the Swift REPL, bundleIdentifier will be nil.

For example, make a file called test.swift containing.

import Foundation

print("\(Bundle.main.bundleIdentifier)")

then run it from the terminal with

swift test.swift

it will print nil

Answer 2

I believe it's because NSBundle has to pull this information from the Info.plist. Remember, the bundleIdentifier method is there on all NSBundle instances, not just the main bundle, and other bundles might not be as well-put-together as the main bundle.

Answer 3

Referring to bundleIdentifier:

The bundle identifier is defined by the CFBundleIdentifier key in the bundle’s information property list.

Because there is a key in the app's .plist file called CFBundleIdentifier could be null:

If you are seeing different key names, right click and choose "Show Row Keys/Values".

In this case, it should be nil.