extension String {

    static func pointer(_ object: AnyObject?) -> String {

        guard let object = object else { return "nil" }

        let opaque: UnsafeMutableRawPointer = Unmanaged.passUnretained(object).toOpaque()

        return String(describing: opaque)

    }

}

​

// Usage:

print("FileManager.default: \(String.pointer(FileManager.default))")

// FileManager.default: 0x00007fff5c287698

​

print("nil: \(String.pointer(nil))")

// nil: nil