Swift - Cannot convert value of type 'UnsafePointer<Any>' to expected argument type 'UnsafePointer<_>'

Question

I am trying to use CommonCrypto (with the help of https://github.com/sergejp/CommonCrypto) for the first time with swift. Here is my code:

UnsafeRawPointer(ivData!.withUnsafeBytes
{(pointer) -> UnsafePointer<Any> in
    let ivBuffer = pointer
})

The error is:

Cannot convert value of type 'UnsafePointer' to expected argument type 'UnsafePointer<_>'

What does the <_> signify? What do I need to do? Thanks.

Solution

It's pointer that it is complaining about. You need to cast it. Here's an example usage, part of creating an MD5 hash:

    var rawBytes = [UInt8](repeating: 0, count: Int(CC_MD5_DIGEST_LENGTH))
    let _ = data.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) in
        CC_MD5(bytes, CC_LONG(data.count), &rawBytes)
    }

Comments

[Nordeast]

Its saying that you cannot convert the type UnsafePointer to a UnsafePointer with a type. I think you need to remove <Any>. Above that it is hard to know with out more code as context.

[ewizard]

i get another error when I do this Reference to generic type 'UnsafePointer' requires arguments in <...> telling me to revert

[ewizard]

great thanks that did it....are the rawBytes always able to be cast as UInt8? I am doing AES encryption

[Don]

You can cast it to whatever you want. To be clear, the reason that you have to cast it is because you are returning it, and preBuffer will be whatever type you are casting it to. Take a look at the Swift 3 answer using Data at stackoverflow.com/questions/37680361/aes-encryption-in-swift‌​, it might provide more insight into how to use it.

[Don]

Side note: you should try to avoid using the force-unwrap operator ! where you can, by using if let or guard let constructs. Colloquially, ! is known as the "crash operator"

[ewizard]

yah im just figuring the optionals out...i have guard where i need it in most places except below i plan on putting that in

[ewizard]

great link...i was looking for something like that for a while to base my encryption function on