title: Objective-C NSString Issue
body: <p>I have global stings as such:</p>
  
  <pre><code>NSString *test = nil;
  NSString *test1 = nil;
  </code></pre>
  
  <p>Do I need to alloc with anything? I do change the String value constantly throughout the program, and i'm getting a EXC_BAD_ACCESS error with segmented control that kills the program.</p>
  
  <p>Any suggestions?</p>
  
  <pre><code>*** Call stack at first throw:
  (
      0   CoreFoundation                      0x00db6be9 __exceptionPreprocess + 185
      1   libobjc.A.dylib                     0x00f0b5c2 objc_exception_throw + 47
      2   CoreFoundation                      0x00db86fb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
      3   CoreFoundation                      0x00d28366 ___forwarding___ + 966
      4   CoreFoundation                      0x00d27f22 _CF_forwarding_prep_0 + 50
      5   tipApp                              0x00005f69 -[tipAppViewController exact] + 54
      6   tipApp                              0x00004907 -[tipAppViewController segmentedControlIndexChanged] + 129
      7   UIKit                               0x002bfa6e -[UIApplication sendAction:to:from:forEvent:] + 119
      8   UIKit                               0x0034e1b5 -[UIControl sendAction:to:forEvent:] + 67
      9   UIKit                               0x00350647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
      10  UIKit                               0x0034e16c -[UIControl sendActionsForControlEvents:] + 49
      11  UIKit                               0x0038d6b2 -[UISegmentedControl setSelectedSegmentIndex:] + 574
      12  UIKit                               0x0039217e -[UISegmentedControl touchesBegan:withEvent:] + 971
      13  UIKit                               0x002e4025 -[UIWindow _sendTouchesForEvent:] + 395
      14  UIKit                               0x002c537a -[UIApplication sendEvent:] + 447
      15  UIKit                               0x002ca732 _UIApplicationHandleEvent + 7576
      16  GraphicsServices                    0x016eca36 PurpleEventCallback + 1550
      17  CoreFoundation                      0x00d98064 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
      18  CoreFoundation                      0x00cf86f7 __CFRunLoopDoSource1 + 215
      19  CoreFoundation                      0x00cf5983 __CFRunLoopRun + 979
      20  CoreFoundation                      0x00cf5240 CFRunLoopRunSpecific + 208
      21  CoreFoundation                      0x00cf5161 CFRunLoopRunInMode + 97
      22  GraphicsServices                    0x016eb268 GSEventRunModal + 217
      23  GraphicsServices                    0x016eb32d GSEventRun + 115
      24  UIKit                               0x002ce42e UIApplicationMain + 1160
      25  tipApp                              0x00001a8c main + 102
      26  tipApp                              0x00001a1d start + 53
  )
  terminate called after throwing an instance of 'NSException'
  </code></pre>
  
  <ul>
  <li>Note this only happens when I start the program out, all strings are nil, and I hit all buttons on the segemented control</li>
  </ul>
  
  <p>I'm just not sure exactly what is going on here</p>