在Swift中页面视图控制器内的视图控制器之间传递数据

Question

Sorry if this particular problem has been asked about, I followed the answers on other threads but none of them seemed to work, but I just started learning Swift so all of this is pretty new to me.

So, I have a text field in two View Controllers and I want the third View Control to display a result based on the input from the other two controllers when I press a button.

I followed this tutorial and placed the text fields, label and button like I said before. I placed my code (which you can see below) inside ViewControl.swift.

The problem is that when I attempt to run it I get a "Thread 1 :EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)" error in the last two lines.

class ViewController: UIViewController {

var a: String = ""
var b: String = ""

@IBOutlet weak var aTextField: UITextField!
@IBOutlet weak var bTextField: UITextField!
@IBOutlet weak var calculateButton: UIButton!
@IBOutlet weak var resultLabel: UILabel!

@IBAction func calculateButtonPressed(_ sender: UIButton) {
    let a = aTextField.text!;  
    let b = bTextField.text!;

I think that the error is from the data not passing between the views (because before I had everything in the same view and it worked fine), but since I only have one ViewController.swift file I couldn't figure out how to use a Segue.

Answer 1

Do not declare same variables multiple times. Remove let before a & b . You have already declared a & b globally and then tried to redeclare it inside IBAction

class ViewController: UIViewController {

var a: String = ""
var b: String = ""

@IBOutlet weak var aTextField: UITextField!
@IBOutlet weak var bTextField: UITextField!
@IBOutlet weak var calculateButton: UIButton!
@IBOutlet weak var resultLabel: UILabel!

@IBAction func calculateButtonPressed(_ sender: UIButton) {
     a = aTextField.text!;  
     b = bTextField.text!;

Answer 2

1. Make sure your control outlets are setted properly.
2. In your two variables a & b are re-declared.Just update your code like below

 @IBAction func calculateButtonPressed(_ sender: UIButton) { self.a = aTextField.text! self.b = bTextField.text! }