title: Proper way to instantiate an NSDecimalNumber from float or double
body: <p>I'm looking for the best way to instantiate an NSDecimalNumber from a double or short.  There are the following NSNumber class and instance methods...</p>
  
  <pre><code>+NSNumber numberWithFloat
  +NSNumber numberWithDouble
  -NSNumber initWithFloat
  -NSNumber initWithDouble
  </code></pre>
  
  <p>but these appear to return NSNumber.  On the other side, NSDecimalNumber defines the following:</p>
  
  <pre><code>+NSDecimalNumber decimalNumberWithMantissa:exponent:isNegative:
  +NSDecimalNumber decimalNumberWithDecimal:
  </code></pre>
  
  <p>There are a few possibilities here on which way to go.  Xcode generates a warning if you have a NSDecimalNumber set to the return value of the NSNumber convenience methods above.</p>
  
  <p>Would appreciate input on the cleanest and correct way to go...</p>