Objectmapper: `Ambigous use of map`when using ImmutableMappable.

Created on 15 Feb 2017 · 4Comments · Source: tristanhimmelman/ObjectMapper

@devxoul Hi! I am trying to use the ImmutableMappable protocol, but there is no explanation in the README of how to use together with nested objects.

I wanna try something simple like this:

struct Father: ImmutableMappable {
    let name: String
    let children: [Child]

    init(map: Map) throws {
        name = try map.value("name")
        children = try map.value("children", using: ArrayTransform<Child>())
    }
}

struct Child: ImmutableMappable {
    let age: Int

    init(map: Map) throws {
        age = try map.value("age")
    }
}

So there is no Transform working with arrays? So I wrote the transformer below inspired by ListTransformer from 'ObjectMapper-Realm'

struct ArrayTransform<T: ImmutableMappable> {}
extension ArrayTransform: TransformType {
    typealias Object = [T]
    typealias JSON = [Any]


    func transformFromJSON(_ value: Any?) -> Object? {
        if let objects = Mapper<T>().mapArray(JSONObject: value) {
            let list = Object()
            list.append(objectsIn: objects)
            return list
        }
        return nil
    }

    public func transformToJSON(_ value: Object?) -> JSON? {
        return value?.flatMap { $0.toJSON() }
    }
}

Results in compilation error: Ambigious use of 'mapArray(JSONObject:)'

My theory is that it is because the compiler finds the method in these two scopes:
public extension Mapper where N: ImmutableMappable
public final class Mapper<N: BaseMappable> {

But since ImmutableMappable inherits from BaseMappable, both functions are valid candidates.

How to use ImmutableMappable for nested objects?

And also, do I have to write a Transformer for that?

Source

Sajjon

Most helpful comment

@Sajjon Btw, AlamofireObjectMapper now supports ImmutableMappable in v4.1

louisdh on 23 Feb 2017

👍2 🎉1

All 4 comments

You don't have to use ArrayTransform stuff. Just do it as following:

init(map: Map) throws {
  // ...
  children = try map.value("children")
}

PS: The reason of the build failure is because you didn't mark `mapArray()` with `try`.

let objects = try Mapper().mapArray(JSONObject: value)
// do something

devxoul on 16 Feb 2017

@devxoul Hey thanks for you reply! Hehe yeah that was easier than I thought! 😅

Regarding your P.S. answer - I still can't get it working! Now I am trying to implement and Alamofire + ObjectMapper extension analogously to AlamofireObjectMapper, but for ImmutableMappable

I still get compilation error Ambigious use of map...., look for the two comments "// Compilation Error" in code below.

What am I doing wrong?

import Foundation
import Alamofire
import ObjectMapper

extension DataRequest {

    enum ErrorCode: Int {
        case noData = 1
        case dataSerializationFailed = 2
    }

    internal static func newError(_ code: ErrorCode, failureReason: String) -> NSError {
        let errorDomain = "com.alamofireobjectmapper.error"

        let userInfo = [NSLocalizedFailureReasonErrorKey: failureReason]
        let returnError = NSError(domain: errorDomain, code: code.rawValue, userInfo: userInfo)

        return returnError
    }

    public static func ObjectMapperSerializer<T: ImmutableMappable>(_ keyPath: String?, mapToObject object: T? = nil, context: MapContext? = nil) -> DataResponseSerializer<T> {
        return DataResponseSerializer { request, response, data, error in
            guard error == nil else {
                return .failure(error!)
            }

            guard let _ = data else {
                let failureReason = "Data could not be serialized. Input data was nil."
                let error = newError(.noData, failureReason: failureReason)
                return .failure(error)
            }

            let jsonResponseSerializer = DataRequest.jsonResponseSerializer(options: .allowFragments)
            let result = jsonResponseSerializer.serializeResponse(request, response, data, error)

            let JSONToMap: Any?
            if let keyPath = keyPath , keyPath.isEmpty == false {
                JSONToMap = (result.value as AnyObject?)?.value(forKeyPath: keyPath)
            } else {
                JSONToMap = result.value
            }

            if let object = object {
                _ = Mapper<T>().map(JSONObject: JSONToMap, toObject: object)
                return .success(object)
            } else {
                do {
                    // Compilation Error: "Amigious user of 'map(JSONObject:)'"
                    let parsedObject = try Mapper<T>(context: context).map(JSONObject: JSONToMap)
                    return .success(parsedObject)
                } catch let error {
                    fatalError("Mapping error: \(error)")
                }
            }

            let failureReason = "ObjectMapper failed to serialize response."
            let error = newError(.dataSerializationFailed, failureReason: failureReason)
            return .failure(error)
        }
    }

    @discardableResult
    public func responseObject<T: ImmutableMappable>(queue: DispatchQueue? = nil, keyPath: String? = nil, mapToObject object: T? = nil, context: MapContext? = nil, completionHandler: @escaping (DataResponse<T>) -> Void) -> Self {
        return response(queue: queue, responseSerializer: DataRequest.ObjectMapperSerializer(keyPath, mapToObject: object, context: context), completionHandler: completionHandler)
    }

    public static func ObjectMapperArraySerializer<T: ImmutableMappable>(_ keyPath: String?, context: MapContext? = nil) -> DataResponseSerializer<[T]> {
        return DataResponseSerializer { request, response, data, error in
            guard error == nil else {
                return .failure(error!)
            }

            guard let _ = data else {
                let failureReason = "Data could not be serialized. Input data was nil."
                let error = newError(.dataSerializationFailed, failureReason: failureReason)
                return .failure(error)
            }

            let jsonResponseSerializer = DataRequest.jsonResponseSerializer(options: .allowFragments)
            let result = jsonResponseSerializer.serializeResponse(request, response, data, error)

            let JSONToMap: Any?
            if let keyPath = keyPath, keyPath.isEmpty == false {
                JSONToMap = (result.value as AnyObject?)?.value(forKeyPath: keyPath)
            } else {
                JSONToMap = result.value
            }

            do {
                // Compilation Error: "Amigious user of 'map(JSONObject:)'"
                let parsedObject = try Mapper<T>(context: context).mapArray(JSONObject: JSONToMap)
                return .success(parsedObject)
            } catch let error {
                fatalError("Failed to map, error: \(error)")
            }

            let failureReason = "ObjectMapper failed to serialize response."
            let error = newError(.dataSerializationFailed, failureReason: failureReason)
            return .failure(error)
        }
    }

    @discardableResult
    public func responseArray<T: ImmutableMappable>(queue: DispatchQueue? = nil, keyPath: String? = nil, context: MapContext? = nil, completionHandler: @escaping (DataResponse<[T]>) -> Void) -> Self {
        return response(queue: queue, responseSerializer: DataRequest.ObjectMapperArraySerializer(keyPath, context: context), completionHandler: completionHandler)
    }
}

Sajjon on 16 Feb 2017

@Sajjon Btw, AlamofireObjectMapper now supports ImmutableMappable in v4.1

louisdh on 23 Feb 2017

👍2 🎉1

Closing this as the new version of AlamofireObjectMapper should take care of the problem. Feel free to comment and I can reopen the ticket if needed.