title: Command /Developer/usr/bin/clang failed with exit code 1
body: <p>I was trying to make a simple Mac Objective-C application with Xcode to keep score of two players playing a simple game with up to 36 scores per player.  It isn't a very practical application because of its limited features, and it's mostly for practice.  I was trying to expand the application a bit with a Preferences window, which would pop up when a menu item was clicked.</p>
  
  <p>I created a file to control the men item, then a nib to pop up when it's clicked.  All of this worked fine, and a new window would pop up.  I put sliders, text fields, etc. on the nib, and connected them to actions.  All of that worked fine.</p>
  
  <p>The problem came when I tried to import the files into my root controller so that I could use the user's choices in the application.</p>
  
  <p>I got the following compiler error:</p>
  
  <pre><code>Command /Developer/usr/bin/clang failed with exit code 1
  </code></pre>
  
  <p>Along with all of this:</p>
  
  <blockquote>
    <p>Ld
    "/Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Products/Debug/SimpleScoreKeeper
    Mac.app/Contents/MacOS/SimpleScoreKeeper Mac" normal x86_64
        cd "/Users/myusername/Dropbox/iphone
    app/SimpleScoreKeeper Mac"
        setenv MACOSX_DEPLOYMENT_TARGET 10.6
        /Developer/usr/bin/clang -arch x86_64 -isysroot
    /Developer/SDKs/MacOSX10.6.sdk
    -L/Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Products/Debug
    -F/Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Products/Debug
    -filelist
    "/Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Intermediates/SimpleScoreKeeper
    Mac.build/Debug/SimpleScoreKeeper
    Mac.build/Objects-normal/x86_64/SimpleScoreKeeper Mac.LinkFileList"
    -mmacosx-version-min=10.6 -framework Cocoa -o
    "/Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Products/Debug/SimpleScoreKeeper
    Mac.app/Contents/MacOS/SimpleScoreKeeper Mac"</p>
    
    <p>ld: duplicate symbol _addScores in
    /Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Intermediates/SimpleScoreKeeper
    Mac.build/Debug/SimpleScoreKeeper
    Mac.build/Objects-normal/x86_64/Prefrences.o and
    /Users/myusername/Library/Developer/Xcode/DerivedData/SimpleScoreKeeper_Mac-bjvjeiybvmwfjpfilvnpezarwkml/Build/Intermediates/SimpleScoreKeeper
    Mac.build/Debug/SimpleScoreKeeper
    Mac.build/Objects-normal/x86_64/RootController.o for architecture
    x86_64 clang: error: linker command failed with exit code 1 (use -v to
    see invocation) Command /Developer/usr/bin/clang failed with exit code
    1</p>
  </blockquote>
  
  <p>The (possibly) related files in my project follow.</p>
  
  <pre><code>RootController.h - All the interface declarations for stuff in the MainMenu.xib window
  RootController.m - Where I need to import the files to
  MainMenu.xib - The nib owned by the RootController class
  Preferences.h - A file I'd want to import, but it won't work.
  Preferences.m - A file I'd (maybe) want to import, but it won't work.
  Preferences.xib - The nib owned by the Preferences class.
  PreferencesMenuController.h - Where I declare the clickPreferences action. (Liked to MainMenu.xib)
  PreferencesMenuController.m - Where I say that clickPreferences opens up Preferences nib.  (Linked to MainMenu.xib)
  </code></pre>
  
  <p>Is there a reason why I'd be getting this error?  Is there something I need to do in the class I'm importing?  Please be pretty detailed, I'm new to the language somight not know how to do certain things.  And if there's anything I need to clarify, let me know.</p>
  
  <p>EDIT:
  Here's the code to the file I can't import.</p>
  
  <pre><code>#import "Preferences.h"
  
  @implementation Preferences
  
  int addScores;
  
  - (IBAction)addScoresToggled
  {
      NSLog(@"addScores was toggled.");
  }
  
  
  - (id)initWithWindow:(NSWindow *)window
  {
      self = [super initWithWindow:window];
      if (self) {
  
      }
  
      return self;
  }
  
  - (void)dealloc
  {
      [super dealloc];
  }
  
  - (void)windowDidLoad
  {
      [super windowDidLoad];
  }
  
  @end
  </code></pre>