Can swift generics be used inside class with generics - swift

Question

I have a protocol call Decodable:
public protocol Decodable {
typealias DecodedType = Self
static func decode(e: Extractor) -> DecodedType?
}
I have a function decode:
public func decode<T: Decodable where T.DecodedType == T>(object: AnyObject) -> T? {
Also, I have a class RestApiResponseParser
class RestApiResponseParser<T where T:Decodable> {
private func createServerModels(response: ServerResponse) -> Result<T> {
var parsingError:NSError?
let link: T? = decode(response)
...
}
...
}
and typealias ServerResponse = [String: AnyObject]
which I try to call as:
let responseParser = RestApiResponseParser<MyModel>(responseData: inputObject as! NSData)
let processError = responseParser.processResponseData()
Unfortunately, I get compile time error:
Does it mean, I can't use generic function in generic class?

Answer 1

Yes, you can use a generic function in a generic class. Your problem is that you are passing a [String: AnyObject] dictionary (which is a struct, and not an AnyObject) into a function that is expecting an AnyObject. It looks like you need to extract the AnyObject from the dictionary using its key:
if let object = response["<insert your key here>"] {
decode(object)
}
Another approach would be to cast your ServerResponse to an NSDictionary which is a class, and can therefore be passed as an AnyObject:
let link: T? = decode(response as NSDictionary)
And btw, the bridging between Dictionary and NSDictionary is not as "seemless" as Apple claims - I have run into instances like this where I can't figure out why Swift isn't able to automatically bridge them for me, and when I have to be explicit. There are inconsistencies like the one that you noted. Your function will take a Dictionary as an argument in once place, but not another, without a clear rationale for why. Perhaps it has something to do with the fact that you are using a typealias, but I'm not sure.