title: Performing valueForKeyPaths against multiple keyPaths
body: <p>Let's say I have an object with some number of properties and I load up 1000s of these objects into an array.  Next, I perform a series of <code>valueForKeyPaths</code> against these properties:</p>
  
  <pre><code>result.property1 = [array valueForKeyPath:@"@sum.property1"];
  result.property2 = [array valueForKeyPath:@"@sum.property2"];
  result.property3 = [array valueForKeyPath:@"@sum.property3"];
  etc...
  </code></pre>
  
  <p>Summing these properties individually seems pretty inefficient.  Is there a better way besides  fast enumerating over the properties and summing them manually?  i.e.</p>
  
  <pre><code>for(Foo* foo in array) {
      result.property1 += foo.property1;
      result.property2 += foo.property2;
      result.property3 += foo.property3;
  }
  </code></pre>