title: Count number of items in an array with a specific property value
body: <p>I have a Person() class:</p>
  
  <pre><code>class Person : NSObject {
  
      var firstName : String
      var lastName : String
      var imageFor : UIImage?
      var isManager : Bool?
  
      init (firstName : String, lastName: String, isManager : Bool) {
          self.firstName = firstName
          self.lastName = lastName
          self.isManager = isManager
      }
  }
  </code></pre>
  
  <p>I have an array of Person()</p>
  
  <pre><code>var peopleArray = [Person]()
  </code></pre>
  
  <p>I want to count the number of people in the array who have </p>
  
  <pre><code> isManager: true
  </code></pre>
  
  <p>I feel this is out there, but I can;t find it, or find the search parameters.</p>
  
  <p>Thanks.</p>