Xcode 4 / gdb /如何简单地观察对象属性？

我有以下代码：

if (labelEast.center.x > (east_oldPosition.x + 50) )
        NSLog(@"Time to switch to previous exercise !");
    else if (labelEast.center.x < (east_oldPosition.x - 50) )
        NSLog(@"Time to switch to next exercise !");

设置断点后,我只是想看看labelEast.center.x(labelEast是一个UILabel对象).由于我在Xcode 4菜单中找不到监视项目,因此我尝试使用gdb.我习惯用po(打印对象)打印变量/对象值.但是现在,我无法显示labelEast中心属性,因为它是从母类继承的.

(gdb) po labelEast.center
There is no member named center.

我不明白为什么gdb说这个,而代码工作正常并看到属性.

因此我有两个问题：

>如何在没有gdb的情况下以图形方式观看这样的属性(就像在Visual Studio中一样)？
>如何用gdb做同样的事情？

非常感谢,
弗朗茨

不幸的是,我尝试了但得到了这个：

po [labelSouth center]

Program received signal EXC_BAD_ACCESS,Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x1a000356 0x343c7d06 in
objc_msgSend_stret () The program being debugged was signaled while in
a function called from GDB. GDB remains in the frame where the signal
was received. To change this behavior use “set unwindonsignal on”
Evaluation of the expression containing the function (objc_msgSend)
will be abandoned.

当我尝试：

(gdb) print labelSouth.center
There is no member named center.

我真的怀疑UILabel没有中心物业.但我怎么能运行代码???