How to pass an Int value to an Objective C function from Swift?

Question

I want to pass an integer value from Swift to Objective C function where I can process it .

Objective C function definition is

 (void)getAllDevices:(NSInteger *)limit :(NSInteger *)offset

The Objective C function is part of an SDK called DemoSDK.

I try to pass the value from Swift using this function call

I tried doing doing this

DemoSDK.getAllDevices(10,10)

But the error that comes is

cannot convert a value of type Int to expected argument of type UnsafeMutablePointer

I am very new to Objective C and this is definitely an amateur question. I want to send an int value to objective C function where I can process the int value. How can I do it? Please help.

Answer 1

The parameters aren't asking for integers, they're asking for references to integers. This is achieved with & in Swift.

var limit = Int()
var offset = Int()

DemoSDK.getAllDevices(&limit, &offset)

Answer 2

There are two similar but different methods which can be mistaken.

• The usual method is

   init(contentsOfURL url: NSURL, encoding enc: UInt) throws 

  The encoding parameter takes an NSStringEncoding value to specify the encoding, for example

   let string = try? String(contentsOfURL:url, encoding:NSUTF8StringEncoding) 

---

• The second method retrieves the encoding from the file by passing a pointer as usedEncoding parameter

   init(contentsOfURL url: NSURL, usedEncoding enc: UnsafeMutablePointer<UInt>) throws 

  The documentation says:

  Upon return, if url is read successfully, contains the encoding used to interpret the data.

  That means you have to pass a pointer which will contain the determined encoding of the file.

   var encoding : NSStringEncoding = 0 let string = try? String(contentsOfURL:url, usedEncoding:&encoding)