Cannot convert value of type 'UInt' to expected argument type 'UnsafeMutablePointer<UInt>'

Question

I am trying to initialize a String from the content accessible by a URL:

actualresponse.response = String(contentsOfURL: url, usedEncoding: NSUTF8StringEncoding)

I get the following error thrown, pointing at the usedEncoding:

Cannot convert value of type 'UInt' to expected argument type 'UnsafeMutablePointer'

Can anyone tell me why this error is thrown and how I can fix it?

Answer 1

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)