RAC tryMap alternative in RxSwift - ios

Question

What is the recommended approach in RxSwift to implement RAC tryMap-like functionality?
The following code is how I do mapping of json objects to an internal response wrapper class. If the response fails to comply with certain conditions, nil will be returned, which turns into an Error Event(tryMap implementation).
extension RACSignal{
func mapToAPIResponse() -> RACSignal{
return tryMap({ (object) -> AnyObject! in
if let data = object as? [String:AnyObject]{
//Some Logic
return data["key"]
}
return nil
})
}
}
How should this be implemented in RxSwift?
Updated-Possible Solution
I came up with following solution for Rx-Swift. Open for better solutions.
extension Observable{
func mapToAPIResponse() -> Observable<APIResponse>{
return map({ (object) in
guard let dictionary = object as? [String:AnyObject] else{
//APIResponseError.InvalidResponseFormat is defined in other class.
throw APIResponseError.InvalidResponseFormat
}
let response = APIResponse()
//Complete API Response
return response
})
}
My conclusion is to use throw inside a map to handle errors.

Answer 1

Your solution is correct, that's why map operator in RxSwift is annotated with throws. Release notes of RxSwift 2 explicitly state this:
Adds support for Swift 2.0 error handling try/do/catch.
You can now just write
API.fetchData(URL)
.map { rawData in
if invalidData(rawData) {
throw myParsingError
}
...
return parsedData
}
Even in `RxCocoa

Answer 2

There is a great way to implement network layer with these set of PODs
RxSwift + Moya/RxSwift + Moya-ObjectMapper/RxSwift
Finally your code for model will looks like
import ObjectMapper
final class Product: Mappable {
var id: String?
var categoryId: String?
var name: String?
func mapping(map: Map) {
id <- map["id"]
categoryId <- map["category_id"]
name <- map["name"]
}
}
And for service
final class ProductService {
class func productWithId(id: String, categoryId: String) -> Observable < Product > {
return networkStubbedProvider
.request(.Product(id, categoryId))
.filterSuccessfulStatusAndRedirectCodes()
.mapObject(Product)
}
}