Why can't LLDB print view.bounds?

Question

Things like this drive me crazy when debugging:

(lldb) p self.bounds
error: unsupported expression with unknown type
error: unsupported expression with unkno         


        

Answer 1

You gonna love Xcode 6.3+

TLDR

(lldb) e @import UIKit
(lldb) po self.view.bounds

LLDB's Objective-C expression parser can now import modules. Any subsequent expression can rely on function and method prototypes defined in the module:

(lldb) p @import Foundation
(lldb) p NSPointFromString(@"{10.0, 20.0}");
(NSPoint) $1 = (x = 10, y = 20)

Before Xcode 6.3, methods and functions without debug information required explicit typecasts to specify their return type. Importing modules allows a developer to avoid the more labor-intensive process of determining and specifying this information manually:

(lldb) p NSPointFromString(@"{10.0, 20.0}");
error: 'NSPointFromString' has unknown return type; cast the call to its declared return type
error: 1 errors parsing expression
(lldb) p (NSPoint)NSPointFromString(@"{10.0, 20.0}”);
(NSPoint) $0 = (x = 10, y = 20)

Other benefits of importing modules include better error messages, access to variadic functions when running on 64-bit devices, and eliminating potentially incorrect inferred argument types.

PS: If you also confuse p vs po

p == print == expression -- == e --
po == expression -O -- == e -O --

-- is the separator between command+flag vs inputs

-O flag is for invoking the object description method