Type 'Int' has no subscript members - ios

Question

I wrote a function:
func rms16(buffer: Int, bufferSize: Int) -> Float
{
let sum: Float = 0.0
let mySize: Int = bufferSize / sizeof(CShort)
var buffer_short: Int = buffer
for var i = 0; i < mySize; i++ {
sum += buffer_short[i] * 2
}
let sqrt1: Float = sqrtf(sum / Float(mySize))
return (sqrt1) / Float(mySize)
}
Above function in a for loop it show me error like this:
Type Int has no subscript members
Anyone tell me how can i fix it?

Answer 1

The buffer_short is an integer variable not an array of integer.
You need to change the first argument of your function to an array of integer, like:
func rms16(buffer: [Int], bufferSize: Int) -> Float
{
let sum: Float = 0.0
let mySize: Int = bufferSize / sizeof(CShort)
var buffer_short = buffer
for var i = 0; i < mySize; i++
{
sum += buffer_short[i] * 2
}
let sqrt1: Float = sqrtf(sum / Float(mySize))
return (sqrt1) / Float(mySize)
}

Answer 2

Your comments indicate that the first parameter should be a pointer to a character buffer. The corresponding Swift type is UnsafePointer<CChar>. Note also that you are multiplying by 2
instead of squaring in your Swift code, and that sum must be
declared as a variable.
So your Swift function would be
func rms16(buffer: UnsafePointer<CChar>, bufferSize: Int) -> Float
{
var sum: Float = 0.0
let mySize = bufferSize / sizeof(CShort)
// Create a pointer to a buffer of `CShort` elements from the given pointer:
let buffer_short = UnsafeBufferPointer<CShort>(start: UnsafePointer(buffer), count: mySize)
for var i = 0; i < mySize; i++ {
sum += pow(Float(buffer_short[i]), 2)
}
let sqrt1 = sqrtf(sum / Float(mySize))
return (sqrt1) / Float(mySize)
}
The summation loop can be reduced (!) to:
let sum = buffer_short.reduce(0.0, combine: { $0 + pow(Float($1), 2)} )