How to call SecItemCopyMatching in Xcode 7 beta 4?

问题:

In previous versions of Xcode 6 and 7 with Swift, this syntax would work:

    var secureItemValue: Unmanaged<AnyObject>?

    let statusCode: OSStatus = SecItemCopyMatching(keychainItemQuery, &secureItemValue)
    if statusCode == errSecSuccess
    {
        let opaquePointer = secureItemValue?.toOpaque()

        let secureItemValueData = Unmanaged<NSData>.fromOpaque(opaquePointer!).takeUnretainedValue()

        // Use secureItemValueData...
    }

However, the SecItemCopyMatching declaration has changed in Xcode 7 beta 4:

OLD: func SecItemCopyMatching(_ query: CFDictionary, _ result: UnsafeMutablePointer<AnyObject?>) -> OSStatus

NEW: func SecItemCopyMatching(_ query: CFDictionary!, _ result: UnsafeMutablePointer<Unmanaged<AnyObject>?>) -> OSStatus

...and now the secureItemValue type does not match.

The mechanism was confusing before to extract the result, and I'm hoping it is somehow easier with the new declaration, but I don't know how to declare the correct type for the secureItemValue variable and extract the result.

回答1:

This works on Xcode 7 beta 4

var dataTypeRef: AnyObject?

    let status: OSStatus = withUnsafeMutablePointer(&dataTypeRef) { SecItemCopyMatching(keychainQuery as CFDictionaryRef, UnsafeMutablePointer($0)) }

    if status == noErr {
        return dataTypeRef as? NSData
    }
    else {
        return nil
    }

回答2:

According to this answer you can just remove Unmanaged<> around AnyObject:

var secureItemValue: AnyObject?

let statusCode: OSStatus = SecItemCopyMatching(keychainItemQuery, &secureItemValue)