Graphics Programs Reference
In-Depth Information
(If you don't see the variables view, find the control above the console.
Click the center button to see both the console and the variables view.)
In the variables view, a pointer variable shows the object's address in memory. (There are
some exceptions; for an
NSString
, the actual string is shown instead.) A variable that is
not a pointer, like
int
, just shows its value.
Click the disclosure button next to
self
. The first item under
self
is its superclass. In
the context of this method,
self
is a pointer to the instance of
WhereamiViewCon-
troller
, so its superclass is
UIViewController
. Clicking the disclosure button
next to
UIViewController
will show the variables
self
inherits from its superclass.
After the superclass, the object's instance variables are listed, which for
Wheream-
iViewController
is just
locationManager
. The breakpoint is set to the line that
creates the instance of
CLLocationManager
and assigns it to
locationManager
.
That line of code has yet to be executed, so
locationManager
is still set to
nil
(
0x0
).
Stepping through code
In addition to giving you a snapshot of the application at a given point, the debugger also
allows you to
step through
your code line by line and see what your application does as
each line executes. The buttons that control the execution are on the
debugger bar
that sits
between the editor area and the debug area (
Figure 4.12
)
.
Figure 4.12 Debugger bar
