title: How to define for a custom unit a long description
body: <p>I try to define my own custom Dimension for pieces. </p>
  
  <pre><code>class UnitPiece: Dimension {
      override static func baseUnit() -&gt; UnitPiece {
          return self.pieces 
       }
  
       static let pieces = UnitPiece(symbol: NSLocalizedString("pcs", comment: "Pieces"), converter: UnitConverterLinear(coefficient: 1))
  }
  </code></pre>
  
  <p>The question, how could I define a new long symbol ("Piece(s)") for the dimension. </p>
  
  <p>I want to us a <code>MeasurmentFormatter</code> for getting the <code>UnitStyle.long</code> form if needed. </p>
  
  <p>Example:</p>
  
  <pre><code>let pcs = Measurement(value: 10, unit: UnitPiece.baseUnit())
  print(pcs)
  
  let formatter = MeasurementFormatter()
  formatter.unitStyle = .long
  formatter.numberFormatter.minimumFractionDigits = 1
  print(formatter.string(from: pcs))
  </code></pre>
  
  <p>Similar to pre defined <code>UnitVolume</code>. There I can explicit get the <code>medium</code>-style or the <code>long</code>-style for the symbols.</p>
  
  <pre><code>let vol = Measurement(value: 10, unit: UnitVolume.gallons)
  print(vol)
  
  let myFormatter = MeasurementFormatter()
  myFormatter.unitStyle = .long
  myFormatter.numberFormatter.minimumFractionDigits = 1
  print(myFormatter.string(from: vol))
  </code></pre>
  
  <p>The <code>code</code> could be copied to a playground.</p>