title: Array how to sort by mutiple property by Swift?
body: <p>I want to sort array data by number value like "90 > 80 > 70 ...> 10".<br>
  But I don't know how to compare mutiple property.<br></p>
  
  <pre><code>struct Item {
     let number1: Double
     let number2: Double
     let number3: Double
  }
  
  let item1 = Item(number1:0, number2:0, number3:10)
  let item2 = Item(number1:20, number2:0, number3:0)
  let item3 = Item(number1:0, number2:30, number3:0)
  let item4 = Item(number1:0, number2:0, number3:40)
  let item5 = Item(number1:0, number2:50, number3:0)
  let item6 = Item(number1:60, number2:0, number3:0)
  let item7 = Item(number1:0, number2:70, number3:0)
  let item8 = Item(number1:0, number2:0, number3:80)
  let item9 = Item(number1:0, number2:90, number3:0)
  
  var array:[Item] = [item1, item2, item3, item4, item5, item6, item7, item8, item9]
  
  array = array.sorted { (item, nextItem) -&gt; Bool in {
       item.number3 &lt; nextItem.number3 //how to add item's number2 &amp; number1 into here.
  }
  </code></pre>