Swift: How to observe if screen is locked in macOS

Question

I want to detect if the user has locked his screen (in macOS) using Swift.

Based on this answer I’ve created the following code:

import Cocoa
import Quartz

if let dict = Quartz.CGSessionCopyCurrentDictionary() as? [String : Any] {
    let locked = dict["CGSSessionScreenIsLocked"]
    print(locked as? String ?? "")
}

...which seems to work fine if I explicitly run the code.

But how is it possible to observe the value so I get notified when the value got changed?

Please change the question title accordingly. – Desdenova Jan 24 '19 at 12:34 — Desdenova, Jan 24 '19 at 12:34
You’re right @Desdenova, I’ve changed it. – ixany Jan 24 '19 at 12:43 — ixany, Jan 24 '19 at 12:43

score 14 · Accepted Answer · edited Dec 24 '22 at 12:29

You can observe distributed notifications. They are not documented.

let dnc = DistributedNotificationCenter.default()

let lockObserver = dnc.addObserver(forName: .init("com.apple.screenIsLocked"),
                               object: nil, queue: .main) { _ in
    NSLog("Screen Locked")
}

let unlockObserver = dnc.addObserver(forName: .init("com.apple.screenIsUnlocked"),
                                 object: nil, queue: .main) { _ in
    NSLog("Screen Unlocked")
}

score 1 · Answer 2 · edited Dec 24 '22 at 12:29

1

With Combine (available on macOS 10.15+):

import Combine

var bag = Set<AnyCancellable>()

let dnc = DistributedNotificationCenter.default()

dnc.publisher(for: Notification.Name(rawValue: "com.apple.screenIsLocked"))
    .sink { _ in print("Screen Locked") }
    .store(in: &bag)

dnc.publisher(for: Notification.Name(rawValue: "com.apple.screenIsUnlocked"))
    .sink { _ in print("Screen Unlocked") }
    .store(in: &bag)

edited Dec 24 '22 at 12:29

Hannes Schneidermayer

4,729
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answered May 30 '20 at 05:30

Steven0351

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Not working for me, nothing is printed – Hannes Schneidermayer Dec 24 '22 at 12:36
@HannesSchneidermayer is your application sandboxed? DistributedNotificationCenter doesn't work with sandboxed applications if I recall correctly. – Steven0351 Jan 05 '23 at 22:08

Swift: How to observe if screen is locked in macOS

2 Answers2

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