Code crashing in during runtime - ios

Question

I am learning swift3 programming but after executing my calculator app its crashing in between. Please check the below code.
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var aLabel: UILabel!
#IBOutlet weak var commmon_button: UIButton!
var a: Int?
var b: Int?
var sum: Int?
var val = ""
#IBOutlet weak var text_feild: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
#IBAction func clik_button(_ sender: UIButton) {
val=String(sender.tag)
text_feild.text = text_feild.text! + val
}
#IBAction func fn_addition(_ sender: UIButton) {
a = Int(text_feild.text!)
}
#IBAction func fn_answer(_ sender: UIButton) {
b = Int(text_feild.text!)
sum = a! + b!
a = 0
b = 0
text_feild.text = nil
text_feild.text = String(sum!)
}
override func viewDidDisappear(_ animated: Bool) {
super.viewDidDisappear(animated)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
During run time i am getting crash at fn_addition by saying Thread 1 breakpoint 2.1

Answer 1

Initiliaze your variables as below
var a = 0
var b = 0
var sum = 0
Replace your methods with below methods.
#IBAction func clik_button(_ sender: UIButton) {
guard let value = String(sender.tag), let text = text_feild.text
else {
return
}
text_feild.text = text + value
}
#IBAction func fn_addition(_ sender: UIButton) {
guard let aValue = Int(text_feild.text)
else{
return
}
a = aValue
}
#IBAction func fn_answer(_ sender: UIButton) {
guard let bValue = Int(text_feild.text)
else{return}
b = bValue
sum = a + b
a = 0
b = 0
text_feild.text = ""
text_feild.text = String(sum)
}
Suggestion: You are using same text field for taking a , b values and for showing sum result. It is better to use two different text fields for taking a and b values separately. Take a label to show sum value.