Swift 4, how to remove two nth charterers from sentence, and start counting each letter in sentence from 1 instead of 0 - swift

Question

I've come outwith this code to remove two charahcters from sentence, however I was wondering how to start counting sentence from 1 when removing characters.
Examplre user enters in each textfield as following:
textfield.text: Hi, thankyou
inputlabelOne.text: 2
inputLabelTwo.text: 5
My code:
var numberOne = Int (InputLabelOne.text)!
var numberTwo = Int (InputLabelTwo.text)!
var text = textfield.text!
var num1 = numberOne
var num2 = numberTwo
if let oneIndex = text.index ((text.startIndex), offsetBy:
num1, limetedBy:(text.endIndex)) ,
let twoIndex = text.index ((text.startIndex), offsetBy: num2,
limetedBy:(text.endIndex)) {
text.remove(at: oneIndex)
text.remove(at: twoIndex)
outputLabel.Text = "sentence with removed letters: \(text)"
}

Answer 1

Firstly, you need to get first index of the string
let startIndex = string.startIndex
Next, you need to get String.Index of the character at first position
let index1 = string.index(startIndex, offsetBy: num1 - 1)
I type minus one because first character has 0 index
Next, you can remove this character
str.remove(at: index1)
Same for the second character
let offset = num1 > num2 ? 1 : 2
let index2 = string.index(startIndex, offsetBy: num2 - offset)
str.remove(at: index2)
If num1 is less than num2 then offset value is 2 because we have already removed one character.
If num1 is greater than num2 then offset value is 1 as for num1.

Answer 2

To avoid the mutating while iterating mistake you have to remove the characters backwards starting at the highest index.
To get 1-based indices just subtract 1 from the offset respectively
var text = "Hi, thankyou"
let inputLabelOne = 2
let inputLabelTwo = 5
if let oneIndex = text.index(text.startIndex, offsetBy: inputLabelOne - 1, limitedBy: text.endIndex),
let twoIndex = text.index(text.startIndex, offsetBy: inputLabelTwo - 1, limitedBy: text.endIndex) {
text.remove(at: twoIndex)
text.remove(at: oneIndex)
}
print(text) // H, hankyou
or as function
func remove(at indices: [Int], from text: inout String) {
let sortedIndices = indices.sorted(by: >)
for index in sortedIndices {
if let anIndex = text.index(text.startIndex, offsetBy: index - 1, limitedBy: text.endIndex) {
text.remove(at: anIndex)
}
}
}
remove(at: [inputLabelOne, inputLabelTwo], from: &text)