How to check a variable's value using a debugger in XCode

Question

How do you use the debugger in XCode to see if a variable is nil?

Greg Sexton · Accepted Answer · 2010-09-18 00:22:26Z

2

If the pointer's address is 0x000000 it's nil.

Hovering over the variable in the debugger should show a tooltip, this will show you the type of the variable, the name and a value. If it is a pointer to an object the value will be the address that it points to. This will be 0x0 if it is nil.

answered Sep 18, 2010 at 0:22

Greg Sexton

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Henrik P. Hessel · Accepted Answer · 2010-09-18 00:20:41Z

2

Just open up the GDB Console and type po myvar or insert a breakpoint after you set your variable and move your cursor over the target variable.

answered Sep 18, 2010 at 0:20

Henrik P. Hessel

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4 Comments

node ninja Over a year ago

It doesn't say anything. If I type something in gdb it doesn't do anything.

Greg Sexton Over a year ago

Are you stopped at a breakpoint whilst running the app? It's probably easier to just type p myvar, the output would look like this if myvar is an NSMutableArray and set to nil, $1 = (NSMutableArray *) 0x0.

Henrik P. Hessel Over a year ago

As Greg mentioned you have to stop at a breakpoint to use both methods

node ninja Over a year ago

Yeah, I'm at a breakpoint. The other method doesn't work either.

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