title: How to use NSDecimalNumber?
body: <p>I'm building a app that needs to perform calculations on money.</p>
  
  <p>I wonder how to properly use NSDecimalNumber, especially how to initialize it from integers, floats &amp; doubles?</p>
  
  <p>I only found it easy to use the <code>-decimalNumberWithString:</code> method. The <code>-initWith...</code> methods are discouraged so that only left the ones with mantissa, but never in any of 7 languages I used before did I need that so I don't know what put there...</p>