title: NSPredicate Filtered childs in array
body: <p>Good day, I'm using new language Apple Swift and using the NSArray:</p>
  
  <pre><code>[
      {
          "Section" : "Title1",
          "Items" :
          [
              {"Nr" : "101"},
              {"Nr" : "201"},
              {"Nr" : "301"},
              {"Nr" : "401"}
          ]
      },
      {
          "Section" : "Title2",
          "Items" :
          [
              {"Nr" : "102"},
              {"Nr" : "202"},
              {"Nr" : "302"}
          ]
      },
      {
          "Section" : "Title3",
          "Items" :
          [
              {"Nr" : "1102"},
              {"Nr" : "2102"},
              {"Nr" : "3102"}
          ]
      }
  ]
  </code></pre>
  
  <p>I want to use search, and display only content what is found</p>
  
  <p>As I understand I have to use the "filteredArrayUsingPredicate" and NSPredicate in swift, so my sample is:</p>
  
  <pre><code>var arr:NSArray = [...] // My array sample goes here
  var pre:NSPredicate = NSPredicate(format: "ANY Items.Nr BEGINSWITH[c] %@", argumentArray: ["20"]) // We a going to search "20" in /Items/Nr
  
  var result:NSArray = arr.filteredArrayUsingPredicate(pre)
  </code></pre>
  
  <p>This is working correct but result is not what I need:</p>
  
  <pre><code>result = 
  [
      {
          "Section" : "Title1",
          "Items" :
          [
              {"Nr" : "101"},
              {"Nr" : "201"},
              {"Nr" : "301"},
              {"Nr" : "401"}
          ]
      },
      {
          "Section" : "Title2",
          "Items" :
          [
              {"Nr" : "102"},
              {"Nr" : "202"},
              {"Nr" : "302"}
          ]
      }
  ]
  </code></pre>
  
  <p>It is display me all section what is contains Imtes with Nr started with "20"</p>
  
  <p>And my question is how to do filter also in Items? The result what I need is have to be:</p>
  
  <pre><code>result = 
  [
      {
          "Section" : "Title1",
          "Items" :
          [
              {"Nr" : "201"}
          ]
      },
      {
          "Section" : "Title2",
          "Items" :
          [
              {"Nr" : "202"}
          ]
      }
  ]
  </code></pre>
  
  <p>I tried to use the SUBQUERY:</p>
  
  <pre><code>"SUBQUERY(Items, $x, $x.Nr BEGINSWITH[c] %@).@count &gt; 0"
  </code></pre>
  
  <p>But this return me the same, if it can calculate the Items, then I thought that it can display me Items/Nr what I found, but I dont know how to write this correct. :)</p>