Continuously append to the end of an array - ios

Question

Each time I press a button I am trying to append that new number to the end of my array. I have tried a ton of different things, but I can't quite get it.
I have tried the append, insert, creating an empty array and so much more.
import UIKit
import Foundation
var num1 = 0
class ViewController: UIViewController {
#IBAction func button(_ sender: UIButton) {
var digitCounts = Array(repeating: 0, count: 10)
var number_list = [1,2,3]
if num1 >= 0 {
digitCounts.insert(3, at: num1)
print(digitCounts)
number_list.append(num1)
num1 += 1
print(num1)
print(number_list)
}
}
the result would look like
starting array [1,2,3] after button pressed first time [1,2,3,4] after
button pressed second time [1,2,3,4,5] after button pressed third time
[1,2,3,4,5,6]

Answer 1

Ok now that you've shown the full code I can see the problem. You are creating new arrays every-time you click the button, but are storing num1 outside of this function.
Try this:
import UIKit
import Foundation
class ViewController: UIViewController {
var num1 = 0
var digitCounts = Array(repeating: 0, count: 10)
var number_list = [1,2,3]
#IBAction func button(_ sender: UIButton) {
if num1 >= 0 {
digitCounts.insert(3, at: num1)
print(digitCounts)
number_list.append(num1)
num1 += 1
print(num1)
print(number_list)
}
}
By storing the arrays as properties of the class, instead of inside the function, they will persist through multiple clicks

Answer 2

you have to make you array global and make changes as follow
import UIKit
import Foundation
var num1 = 0
class ViewController: UIViewController {
var number_list = [1,2,3]
#IBAction func button(_ sender: UIButton) {
var number = number_list.last ?? 0
number += 1
number_list.append(number)
print(number_list)
}
}

Answer 3

If you're not multithreading, a simple solution is to remember the last number instead of having to check the last element in the array:
class ViewController: UIViewController {
var number_list = [1, 2, 3]
var num1 = 3
#IBAction func button(_ sender: UIButton) {
number += 1
number_list.append(number)
print(number_list)
}
}

Answer 4

First of all you should declare var number_list as a ViewController's property:
class ViewController: UIViewController {
var number_list = [1,2,3]
}
Otherwise var number_list with it's default value will be created each time when button(_ sender:) is calling.
And use the following handler for your button:
#IBAction func button(_ sender: UIButton) {
number_list += number_list.last.flatMap { [$0+1] } ?? []
print(number_list)
}
All code in this post was tested in Xcode 10.2.1. I used Swift 5.