title: Default parameter values error: "instance member cannot be used on type viewcontroller"
body: <p>In my view controller:</p>
  
  <pre><code>class FoodAddViewController: UIViewController, UIPickerViewDataSource, UITextFieldDelegate, UIPickerViewDelegate {
  
      let TAG = "FoodAddViewController"
  
      // Retreive the managedObjectContext from AppDelegate
      let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
  
      @IBOutlet weak var foodName: UITextField!
  
      @IBOutlet weak var foodPortion: UITextField!
  
      @IBOutlet weak var foodCalories: UITextField!
  
      @IBOutlet weak var foodUnit: UILabel!
  
      @IBOutlet weak var unitPicker: UIPickerView!
  
      @IBOutlet weak var unitPickerViewContainer: UIVisualEffectView!
  
      /*
          unrelated code has been ommited
      */
      func validateAllTextFields(textFields: [UITextField] = [foodName as UITextField, foodPortion, foodCalories]) -&gt; Bool {
  
          var result = true
          for textField in textFields {
              result = validateTextField(textField) &amp;&amp; result
          }
          return result
      }
  
      func validateTextField(textField: UITextField) -&gt; Bool{
          let correctColor = UIColor.redColor().CGColor, normalColor = UIColor.blackColor().CGColor
          var correct = true
  
          if textField == foodPortion || textField == foodCalories{
              if !Misc.isInteger(textField.text!){
                  correct = false
              }
          }
          if textField.text!.isEmpty {
              correct = false
          }
  
          textField.layer.borderColor = correct ? normalColor : correctColor
  
          return correct
      }
  }
  </code></pre>
  
  <p>I have a few textfields, and in my validateTextField can verify one at a time, and I want my validateAllTextFields be able to verify a give list of textfield by checking them one by one, if the list is not given, I want to check a given default list that contains all three textfield. </p>
  
  <p>The code I imagine to be something like:</p>
  
  <pre><code>func validateAllTextFields(textFields: [UITextField] = [foodName as UITextField, foodPortion, foodCalories]) -&gt; Bool {
  
      var result = true
      for textField in textFields {
          result = validateTextField(textField) &amp;&amp; result
      }
      return result
  }
  </code></pre>
  
  <p>However Xcode gives an error back:</p>
  
  <blockquote>
    <p>instance member cannot be used on type viewcontroller</p>
  </blockquote>
  
  <p>What's the cause and how to fix?</p>