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xcodensnotificationcenterlldb

Xcode debugger (lldb) get object description from memory address

Little-known fact: It is now possible, in Xcode, while paused in the debugger, to introspect the notification center to learn what objects are registered to receive what notifications:

(lldb) po NotificationCenter.default

<NSNotificationCenter:0x6040000d40b0>
Name, Object, Observer, Options
com.apple.accessibility.reduce.motion.status, 0x10b126190, 0x7fc795700140, 1001
com.apple.accessibility.asst.scanner.status, 0x10b126190, 0x7fc795700140, 1001
// ... etc. ...

Very nice, but how do I go from obtaining the memory address 0x7fc795700140 to learning what object that is?

EDIT I'm leaving this question here, but I think the correct answer is the kind of thing shown at LLDB (Swift): Casting Raw Address into Usable Type

Solution

  • po works for addresses (In Objective-C/Mac context, at least)

    e.g.:

    (lldb) po [NSNotificationCenter defaultCenter]

    NSWindowDidResizeNotification, 0x7fff9a0e98e0, 0x6100001246a0, 1400

    (lldb) po 0x6100001246a0

    ExpandOneView: 0x6100001246a0