What does it mean , Illegal instruction: 4? [duplicate] - swift

Question

This question already has an answer here:
Swift - fatal error: Array index out of range
(1 answer)
Closed 3 years ago.
Below is the small code snippet written in swift,gives below error, although looking at code nothing seems wrong.
Fatal error: Index out of range
Illegal instruction: 4
Not clear to me what is the exact cause of problem ? Would be really helpful if someone can share insights on it.
func getBinary(ValueInDecimal:Int) -> [Int]
{
var valueToPlayWith = ValueInDecimal
var aryBinary = [Int]()
var i:Int = 0
while valueToPlayWith != 0 {
aryBinary[i] = valueToPlayWith % 2
valueToPlayWith = valueToPlayWith / 2
i = i + 1
}
return aryBinary
}
// calling of function
let aryBin = getBinary(ValueInDecimal:10)
print(aryBin)
Expected answer is binary value of passed decimal number in array of 0s and 1s.
So I think if I will use it like this then syntax array[i] = value will work.
func getBinary(ValueInDecimal:Int) -> [Int:Int]
{
var valueToPlayWith = ValueInDecimal
var aryBinary = [Int:Int]()
var i:Int = 0
while valueToPlayWith != 0 {
aryBinary[i] = valueToPlayWith % 2
valueToPlayWith = valueToPlayWith / 2
i = i + 1
}
return aryBinary
}
let aryBin = getBinary(ValueInDecimal:10)
print(aryBin)

Answer 1

This is an empty array
var aryBinary = [Int]()
so this will crash as index 0 doesn't exist
aryBinary[i] = valueToPlayWith % 2
Fatal error: Index out of range
You may need
func getBinary(_ valueInDecimal:Int) -> [Int] {
var valueToPlayWith = valueInDecimal
var aryBinary = [Int]()
while valueToPlayWith != 0 {
aryBinary.append(valueToPlayWith % 2)
valueToPlayWith = valueToPlayWith / 2
}
return aryBinary
}
let aryBin = getBinary(10)
print(aryBin) /// [0, 1, 0, 1]