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swiftcore-foundation

Recasting 'UnsafePointer<Void>' to 'CFHTTPMessageRef'

I've tried dozens of things to get this right and just can't come up with anything that works. Can anyone tell me what's wrong with the following Swift code:

let incomingRequest: CFHTTPMessageRef? = CFDictionaryGetValue(self.incomingRequests as CFMutableDictionaryRef, unsafeAddressOf(incomingFileHandle!)) as CFHTTPMessageRef

The code above gives the error message: 'UnsafePointer<Void>' is not convertible to 'CFHTTPMessageRef'

I guess what I don't understand is how do I convert an 'UnsafePointer' returned by a Core Foundation function to the pointer type it should be (i.e. CFHTTPMessageRef in this case). How do I find documentation on how to do this. I've read everything I can find, but nothing so far explains how to recast return values to what they should have been in the first place. This has to be documented somewhere, doesn't it?

EDIT

Here's the code I'm having trouble with:

let incomingRequest = CFDictionaryGetValue(self.incomingRequests as CFMutableDictionaryRef, unsafeAddressOf(incomingFileHandle!))
        unsafeBitCast(incomingRequest, CFHTTPMessageRef.self)
if (incomingRequest != nil) {
let success: Boolean = CFHTTPMessageAppendBytes(incomingRequest as CFHTTPMessageRef, unsafeAddressOf(data!.bytes) as UnsafePointer<UInt8>, data!.length)
if success { // Do something... }

The CFHTTPMessageAppendBytes call still gives a "Type 'UnsafePointer' does not conform to protocol 'AnyObject'". And the following 'if' check for 'success' complains that "Type 'Boolean' doesn not conform to protocol 'BooleanType'". What the heck is that about? Boolean isn't a Boolean type?

I find the strict type checking of Swift extremely frustrating. So far it is far more difficult to code in than Obj-C, C, or any of the other languages I've used. I'm sure it's because I just don't get it, or haven't found the right documentation, but this is really driving me crazy.

Solution

  • Use unsafeBitCast. As following example:

    import Foundation
var x = "1"
var dict : NSMutableDictionary = [x: "2"]
var y = CFDictionaryGetValue(dict as CFMutableDictionaryRef, unsafeAddressOf(x))
let str: NSString = unsafeBitCast(y, NSString.self)
str == "2"

    FYI: There is one quora related with unsafeBitCast. http://www.quora.com/Why-does-Swift-not-allow-implicit-type-conversion