title: Debugging basics
body: <p>I'm new in programming, and I'm trying to code my first app in swift.
  I've got my App crashing at runtime, but I'm not able to understand a word in Xcode debug navigator.
  I can't post a screenshot as this is my first post at StackOverFlow.</p>
  
  <p>Could you help me to interpret XCode6 (Swift) crash console.
  How can I point toward the cause of a crash?
  What do I have to focus on ?</p>
  
  <p>Sorry for this general question but I was not able to find some clear documentation on debugging in XCode 6.</p>
  
  <p>Thanks for your help</p>
  
  <p>Here is what the console displays (after removing the breakpoint) :</p>
  
  <blockquote>
    <p>(Entrée dans la fonction, numberOfSectionsInTableView) (Entrée dans la
    fonction, tableView(<em>:numberOfRowsInSection:)) (Entrée dans la
    fonction, numberOfSectionsInTableView) (Entrée dans la fonction,
    tableView(</em>:numberOfRowsInSection:)) (Entrée dans la fonction,
    numberOfSectionsInTableView) (Entrée dans la fonction,
    tableView(<em>:numberOfRowsInSection:)) (Entrée dans la fonction,
    numberOfSectionsInTableView) (Entrée dans la fonction,
    tableView(</em>:numberOfRowsInSection:)) 2015-04-14 12:05:12.659
    ListeDeCourses[20984:2203737] -[ListeDeCourses.AjoutViewController
    ButtonAdd:]: unrecognized selector sent to instance 0x7fe178739770
    2015-04-14 12:05:12.663 ListeDeCourses[20984:2203737] <strong>* Terminating
    app due to uncaught exception 'NSInvalidArgumentException', reason:
    '-[ListeDeCourses.AjoutViewController ButtonAdd:]: unrecognized
    selector sent to instance 0x7fe178739770'
    *</strong> First throw call stack: (     0   CoreFoundation                      0x0000000106ecff35 <strong>exceptionPreprocess + 165  1   libobjc.A.dylib<br>
    0x0000000108a13bb7 objc_exception_throw + 45  2   CoreFoundation<br>
    0x0000000106ed704d -[NSObject(NSObject) doesNotRecognizeSelector:] +
    205   3   CoreFoundation                      0x0000000106e2f27c
    ___forwarding_</strong> + 988    4   CoreFoundation                      0x0000000106e2ee18 _CF_forwarding_prep_0 + 120  5   UIKit<br>
    0x000000010775c8be -[UIApplication sendAction:to:from:forEvent:] + 75
      6   UIKit                               0x0000000107863410
    -[UIControl _sendActionsForEvents:withEvent:] + 467   7   UIKit                               0x00000001078627df -[UIControl touchesEnded:withEvent:] + 522   8<br>
    UIKit                               0x00000001077a2308 -[UIWindow
    _sendTouchesForEvent:] + 735  9   UIKit                               0x00000001077a2c33 -[UIWindow sendEvent:] + 683     10  UIKit<br>
    0x000000010776f9b1 -[UIApplication sendEvent:] + 246  11  UIKit<br>
    0x000000010777ca7d _UIApplicationHandleEventFromQueueEvent + 17370    12
    UIKit                               0x0000000107758103
    _UIApplicationHandleEventQueue + 1961     13  CoreFoundation                      0x0000000106e05551
    <strong>CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION</strong> + 17   14  CoreFoundation                      0x0000000106dfb41d
    __CFRunLoopDoSources0 + 269   15  CoreFoundation                      0x0000000106dfaa54 __CFRunLoopRun + 868     16  CoreFoundation<br>
    0x0000000106dfa486 CFRunLoopRunSpecific + 470     17  GraphicsServices<br>
    0x000000010afc69f0 GSEventRunModal + 161  18  UIKit<br>
    0x000000010775b420 UIApplicationMain + 1282   19  ListeDeCourses<br>
    0x0000000106ce243e top_level_code + 78    20  ListeDeCourses<br>
    0x0000000106ce247a main + 42  21  libdyld.dylib<br>
    0x00000001091ed145 start + 1  22  ???<br>
    0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with
    uncaught exception of type NSException (lldb)</p>
  </blockquote>
  
  <p>and this is what is displayed with an exception breakpoint :</p>
  
  <blockquote>
    <p>(Entrée dans la fonction, numberOfSectionsInTableView) (Entrée dans la
    fonction, tableView(<em>:numberOfRowsInSection:)) (Entrée dans la
    fonction, numberOfSectionsInTableView) (Entrée dans la fonction,
    tableView(</em>:numberOfRowsInSection:)) (Entrée dans la fonction,
    numberOfSectionsInTableView) (Entrée dans la fonction,
    tableView(<em>:numberOfRowsInSection:)) (Entrée dans la fonction,
    numberOfSectionsInTableView) (Entrée dans la fonction,
    tableView(</em>:numberOfRowsInSection:)) 2015-04-14 12:10:28.285
    ListeDeCourses[21044:2208020] -[ListeDeCourses.AjoutViewController
    ButtonAdd:]: unrecognized selector sent to instance 0x7fcf5a748630
    (lldb)</p>
  </blockquote>
  
  <p>Finally a screen shot:
  <img src="https://i.stack.imgur.com/sMP74.png" alt="enter image description here"></p>