po in LLDB with swift

Question

How can I plot out variable\'s value in a Swift App with LLDB?

Earlier it was like po variable_name

Now I usually get some nasty error, like:

Answer 1

I have made a few tests to figure out how it works with Swift, results surprised me a bit. With ObjC objects po calls debugDescription which by default calls description. That is clear. Unfortunately the same doesn't apply while working with Swift classes. I focused on objects rather than on printing single variables.

To make it working (po command in lldb) I had to override description. Below code I used for testing:

class Test : NSObject
{
    var name : String?
    var surname : String?

    override var debugDescription : String{
        return "debugDescription method"
    }

    override var description : String {
        return "description Method"
    }
}

Testing:

let test = Test()
test.name = "name"
test.surname = "surname"

(lldb) po test
description Method

(lldb) p test
(DebugTest.Test) $R1 = 0x00007fce11404860 {
  ObjectiveC.NSObject = {
    isa = DebugTest.Test
  }
  name = "name"
  surname = "surname"
}

(lldb) po dump(test)
▿ DebugTest.Test #0
  - super: debugDescription method
  ▿ name: name
    - Some: name
  ▿ surname: surname
    - Some: surname
description Method

(lldb) po print(test)
description Method

The thing that surprised me is that po on Swift objects calls description rather than debugDescription that differs from ObjC.

EDIT

To make it acting like with ObjC, Your class have to implement CustomDebugStringConvertible and then po will call debugDescription, which by default calls description. The only thing which have to be changed in my example would be adding:

class Test : NSObject, CustomDebugStringConvertible

Reference

Checked with XCode 7.0.1 and iOS SDK 9, Swift 2.0