Using the Debugger
When an application is launched from Xcode, the debugger is attached to it. The debugger monitors the current state of the application, like what method it is currently executing and the values of the variables that are accessible from that method. Using the debugger can help you understand what an application is actually doing, which, in turn, helps you find and fix bugs.
One way to use the debugger is to set a breakpoint. Setting a breakpoint on a line of code pauses the execution of the application at that line (before it executes). Then you can execute the subsequent code line by line. This is useful when your application is not doing what you expected and you need to isolate the problem. ...