Google Books API parsing - ios

Question

So I'm trying to parse Google Books API respond. I want to get title, description, thumbnailUrl, authors and published data. Here is the problem :
func getBooksFrom(completion: #escaping (Result<[[String: AnyObject]]>) -> Void) {
URLSession.shared.dataTask(with: url) { (data, response, error) in
guard error == nil else { return completion(.Error(error!.localizedDescription)) }
guard let data = data else { return
completion(.Error(error!.localizedDescription)) }
do {
if let json = try JSONSerialization.jsonObject(with: data, options: [.mutableContainers]) as? [String: AnyObject] {
if let items = json["items"] as? [[String: AnyObject]] {
DispatchQueue.main.async {
completion(.Succes(items))
}
}
}
} catch let error {
print(error.localizedDescription)
return completion(.Error(error.localizedDescription))
}
}.resume()
}
And on my View Controller in the ViewDidLoad i have
let service = ApiService()
service.getBooksFrom { (result) in
switch result {
case .Succes(let data):
self.parseData(array: data)
case .Error(let message):
self.showAlertWith(title: "Error", and: message)
}
}
So that's pretty simple parsing, but...
When I want to map items into Book Object i have to :
func parseData(_ data: [[String: AnyObject]]) -> [Book]{
for item in data {
if let volumeInfo = item["volumeInfo"] as? [String: AnyObject] {
let books = data.map { (jsonDictionary) -> Book in
let title = volumeInfo["title"] as? String ?? ""
let publishedData = volumeInfo["publishedDate"] as? String ?? ""
let authors = volumeInfo["authors"] as? [String] ?? [""]
let description = volumeInfo["description"] as? String ?? ""
let newBook = Book(title: title, publishedData: publishedData, description: description)
return newBook
}
return books
}
}
return [Book]()
}
Which is super awful way to do it.. You have to return Book on the bottom, because of the for-loop, and
VolumeInfo is next Dictionary, so I really don't know exactly how to map it and get for example authors, because it's next Array..
One sample JSON object:
{
"items":[
{
"volumeInfo":{
"title":"The Ancestor's Tale",
"subtitle":"A Pilgrimage to the Dawn of Life",
"authors":[
"Richard Dawkins",
"Yan Wong"
]
"publishedDate":"2016-04-28",
"description":"A fully updated ",
"imageLinks":{
"smallThumbnail":"http://books.google.com/books/content?id=vzbVCQAAQBAJ&printsec=frontcover&img=1&zoom=5&edge=curl&source=gbs_api",
"thumbnail":"http://books.google.com/books/content?id=vzbVCQAAQBAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api"
}
}
]}
So this is quite simple when you have array of String : Value, but how should you map in proper way, when you have for example dictionaries in dictionary VolumeInfo or array of strings like authors?

Answer 1

I personally find the way to parse objects in swift with URLSession relatively clumsy. Whenever I can I use Alamofire in combination with the AlamofireObjectMapper.
This allows you to create a simple object. For example:
class Book: Mappable {
var title: String?
var subtitle: String?
var description: String?
required init?(map: Map){
}
func mapping(map: Map) {
title <- map["title"]
subtitle <- map["subtitle"]
description <- map["description"]
}
}
When you make a request, you can then use the responseObject method to directly parse your object and assign the proper types.
Alamofire.request(URL).responseObject { (response: DataResponse<Book>) in
let book = response.result.value
print(book?.title)
}
For this example, I simply parsed only one book. But the concept can also be easily extended to arrays or nested json objects. I personally find this leads to much cleaner code than using URLSession directly.