To check memory related issues in iOS applications, in xcode there is an option to enable zombie, which keeps tracks on the memory issues. The below steps explains you about enabling zombie in Xcode 4 and above.
1) Press command + Alt + R.
2) A window is opened, goto to Diagnostics Tab.
3) Select the check box, for “Enable zombie objects”.
Thats it, this will enable the NSZombie and start testing your application