Swift, C++ and structs

Question

I need to send a Swift struct consisting of two floats to some C++ code.

Swift struct

struct ComplexNumber
{
   var real: Float
   var imaginary: Float
}

C++ method signature

void processComplexNumbers(const ComplexNumber *complexNumbers, const int *indices);

I have typedef'd the same struct in C++.

When I try to call this from Swift I get the error cannot convert value from UnsafePointer<ComplexNumber> to expected argument type UnsafePointer<ComplexNumber> . The following code is a simple illustration of this error.

var samples = [ComplexNumber]()
var indices = [Int]()
var samplesPtr = UnsafePoiner<ComplexNumber>(samples)
var indices = UnsafePoiner<Int>(indices)
processComplexNumbers(samples, indices)

Why can't I get this to work and is there a workaround?

Answer 1

Two problems:

You can use a C-struct in Swift not vice-versa (Swift 2.1)

I had to define an identical struct called ComplexNumbersF (F is for float) in C that I used for the unsafe pointer call.

var samples = [ComplexNumber]()
var samplesPtr = UnsafePoiner<ComplexNumberF>(samples)

Int isn't int.

If you want to use Swift's Int the C++ equivalent is long . If you use a C++ int every other value will be 0. Alternatively you can use Swift's Int32 , but that wasn't really desirable in my case.