title: Inline function "undefined symbols" error
body: <p>I want to write an inline function, but I get an error. How can I fix it?</p>
  
  <p>Error information:</p>
  
  <pre class="lang-none prettyprint-override"><code>Undefined symbols for architecture i386:
    "_XYInRect", referenced from:
        -[BeginAnimation ccTouchesEnded:withEvent:] in BeginAnimation.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>CGPoint location = CGPointMake(60, 350);
  
  if (XYInRect(location, 53, 338, 263, 369)) {
  
  }
  
  inline BOOL XYInRect(CGPoint location, float MixX, float MixY, float MaxX ,float MaxY){
      if (location.x &gt;MixX &amp;&amp; location.y &gt;MixY &amp;&amp; location.x &lt;MaxX &amp;&amp; location.y &lt;MaxY) {
          return YES;
      } else {
          return NO;
  
      }
  }
  </code></pre>