RetrievingJSONObjectExample.md

Retrieving a JSON object example

Let's say you need to retrieve this JSON from an server, http://localhost:8000/<continent>.json:

{
  "cities": [{
    "name": "Paris"
  }, {
    "name": "London"
  }]
}

The Swift model for a city could look something like this:

struct City {
  let name: String
}

Some basic parsing logic:

extension City {
  init?(jsonDictionary: [String : Any]) {
    guard let parsedName = jsonDictionary["name"] as? String else {
      return nil
    }
    name = parsedName
  }
}

Defining a Resource

A CitiesResource can be created to define where the cities will come from and how the base endpoint should be parsed:

private let baseURL = URL(string: "http://localhost:8000/")!

enum CitiesResourceError: Error {
  case parsingFailed
}

struct CitiesResource: NetworkJSONDictionaryResourceType {
  typealias Model = [City]

  let url: URL

  init(continent: String) {
    url = baseURL.appendingPathComponent("\(continent).json")
  }

  // MARK: JSONDictionaryResourceType
  func model(from jsonDictionary: [String : Any]) throws -> Model {
    guard let
      citiesJSONArray = jsonDictionary["cities"] as? [[String: Any]]
      else {
        throw CitiesResourceError.parsingFailed
    }
    return citiesJSONArray.flatMap(City.init)
  }

}

Retrieving the resource

Use the provided NetworkDataResourceService to retrieve your CitiesResource from a web service:

let europeResource = CitiesResource(continent: "europe")
let networkService = NetworkDataResourceService()
networkService.fetch(resource: europeResource) { networkResponse in
  // do something with the networkResponse
}

OR

Define a typealias for conveniency if you using (NS)Operations:

private typealias CitiesNetworkResourceOperation = ResourceOperation<GenericNetworkDataResourceService<CitiesResource>>

Create the operation using a CitiesResource

let europeResource = CitiesResource(continent: "europe")
let citiesNetworkResourceOperation = CitiesNetworkResourceOperation(resource: europeResource) { operation, networkResponse in
  // do something with the networkResponse
}

Add the operation to some queue:

let operationQueue = OperationQueue()
operationQueue.addOperation(citiesNetworkResourceOperation)