Xcode LLDB Print Statements Fail - NSUndoManager

Question

I have a breakpoint set and want to print my UITextField's superview. I type po myTextField.superview but I receive the following error:

error: instance method 'undoManager' has incompatible result types in different translation units ('id' vs. 'NSUndoManager *')
note: instance method 'undoManager' also declared here
error: 1 errors parsing expression

What does this mean and how can I print my superview? I found a link that provides a janky workaround in code: http://openradar.io/15890965, but I would like a better solution.

Yammer

Same story here: I try po tableView.gestureRecognizers on a category of UITableView. – Recluse

I have seen this error many times when trying to po frame, bounds, recursiveDescription, constraints, etc. (only built-in methods). Seems to be a crippling xcode/lldb bug. – Viridis

Answer 1

People of the world: I have an answer!

To dodge all UIKit errors: Before typing your po statement, type the line -- expr @import UIKit

If you want to turn this on for your app globally, then add the following breakpoint in your app delegate:

Thanks to Craig Hockenberry and Steve Streza for the update (found here).

Yammer

This article tells you how to turn this on for all projects: merowing.info/2015/12/… – Yammer

Answer 2

The solution I use to prevent this error while debugging is to explicitly cast everything.

In your case I would do

po [(UITextField *)myTextField superView]

Cal

From initial testing, this seems to work for me. However, the 2nd comment in the link above (openradar.io/15890965) claims that it happens for them, even when explicitly casting. Anyone else want to chime in? – Yammer

I tried explicitly casting and still get this error. e.g. po (NSString *)[((IBAdBannerView *)adView) recursiveDescription] – Clupeid

Answer 3

Do you have any custom accessor methods for 'myTextField'? I have seen this same issue a number of times and it is usually caused by the po trying to print a property for an object that gets initialized the first time its getter is called. For example, if I try to run 'po self.imageView.contentMode' on a UITableViewCell I get that same error. Try moving your breakpoint to a point in the code where you know that 'myTextField' has been fully initialized.

Thickwitted

I do not have a custom accessor method for myTextField. Good thought though. – Yammer

Answer 4

Does myTextField really point to a UITextField? That's one reason this error will show up. For instance, the following code will compile, and if I set a breakpoint on the third line, I can enter po b.superview to reproduce the error you saw.

NSString *a = @"not a view";
UITextField *b = (UITextField *)a;
UIView *view = b.superview;

Try typing po [myTextField class] at your LLDB prompt to see if it's actually a UITextField. It could be another type of object, or nil.

Female

myTextField does point to a UITextField (through an outlet). – Yammer

Answer 5

I got this error in Xcode 5.1.1 and fixed it by quitting Xcode 5.1.1 and trying Xcode 6. Rebooting Xcode 5.1.1 for Xcode 5.1.1 may also work for some people.

Clupeid

I have not yet found this error with Xcode 6, so Apple may have fixed it. It'll take some more time before we're sure though. – Yammer