Default parameter values error: “instance member cannot be used on type viewcontroller”

问题

In my view controller:

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]) -> Bool {

        var result = true
        for textField in textFields {
            result = validateTextField(textField) && result
        }
        return result
    }

    func validateTextField(textField: UITextField) -> 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
    }
}

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.

The code I imagine to be something like:

func validateAllTextFields(textFields: [UITextField] = [foodName as UITextField, foodPortion, foodCalories]) -> Bool {

    var result = true
    for textField in textFields {
        result = validateTextField(textField) && result
    }
    return result
}

However Xcode gives an error back:

instance member cannot be used on type viewcontroller

What's the cause and how to fix?

回答1:

You cannot use instance variables in function declarations. Call the function with your textFields array and pass the parameters.

func validateAllTextFields(textFields: [UITextField] ) -> Bool {

    var result = true
    for textField in textFields {
        result = validateTextField(textField) && result
    }
    return result
}

somehwere in your class:

validateAllTextFields(textFields: [foodName, foodPortion, foodCalories])

Or you check inside of your function if textFields is empty and than u use the instance variables

func validateAllTextFields(textFields: [UITextField] ) -> Bool {
    if textFields.count == 0 {
        textFields = [foodName, foodPortion, foodCalories]
    }
    var result = true
    for textField in textFields {
        result = validateTextField(textField) && result
    }
    return result
}

来源：https://stackoverflow.com/questions/32884023/default-parameter-values-error-instance-member-cannot-be-used-on-type-viewcont

标签

ios

uiviewcontroller

uitextfield

swift2