title: SWIFT 3 Predicate for NSArray not working properly with numbers
body: <p>I am learning to use predicates for filtering. I found a tutorial, but one aspect is not working for me in Swift 3. Here is some specific code:</p>
  
  <pre><code>let ageIs33Predicate01 = NSPredicate(format: "age = 33") //THIS WORKS
  let ageIs33Predicate02 = NSPredicate(format: "%K = 33", "age") //THIS WORKS
  let ageIs33Predicate03 = NSPredicate(format: "%K = %@", "age","33") //THIS DOESN'T WORK
  let ageIs33Predicate04 = NSPredicate(format: "age = %@","33") //THIS DOESN'T WORK
  </code></pre>
  
  <p>All 4 compile, but the last 2 produce no results even though I have a case where age = 33. Here is the test complete test code from the tutorial:</p>
  
  <pre><code>import Foundation
  
  class Person: NSObject {
      let firstName: String
      let lastName: String
      let age: Int
  
      init(firstName: String, lastName: String, age: Int) {
          self.firstName = firstName
          self.lastName = lastName
          self.age = age
      }
  
      override var description: String {
          return "\(firstName) \(lastName)"
      }
  }
  
  let alice = Person(firstName: "Alice", lastName: "Smith", age: 24)
  let bob = Person(firstName: "Bob", lastName: "Jones", age: 27)
  let charlie = Person(firstName: "Charlie", lastName: "Smith", age: 33)
  let quentin = Person(firstName: "Quentin", lastName: "Alberts", age: 31)
  let people = [alice, bob, charlie, quentin]
  
  let ageIs33Predicate01 = NSPredicate(format: "age = 33")
  let ageIs33Predicate02 = NSPredicate(format: "%K = 33", "age")
  let ageIs33Predicate03 = NSPredicate(format: "%K = %@", "age","33")
  let ageIs33Predicate04 = NSPredicate(format: "age = %@","33")
  
  (people as NSArray).filtered(using: ageIs33Predicate01)
  // ["Charlie Smith"]
  
  (people as NSArray).filtered(using: ageIs33Predicate02)
  // ["Charlie Smith"]
  
  (people as NSArray).filtered(using: ageIs33Predicate03)
  // []
  
  (people as NSArray).filtered(using: ageIs33Predicate04)
  // []
  </code></pre>
  
  <p>What am I doing wrong? Thanks.</p>