Swift 4 : Decode array

Question

I want to easily decode a JSON file with Decode protocol from Swift 4 on Xcode 9. This my question : How to decode à JSON like this:

[
  {
    "name": "My first Catalog",
    "order": 0,
    "products": [
      {
        "product": {
          "title": "product title",
          "reference": "ref"
        }
      }
    ]
  }
]

I try this but it's doesn't work

fileprivate struct Catalog: Codable {
    var name: String
    var order: Int
    var product: [Product]
}

fileprivate struct Product: Codable {
    var title: String
    var reference: String
}

...

// JSON Decoder
        do {
            let jsonData = try Data(contentsOf: URL(fileURLWithPath: filePath), options: .alwaysMapped)

            let jsonDecoder = JSONDecoder()

            let jsonCatalogs = try? jsonDecoder.decode(Array<Catalog>.self,
                                                       from: jsonData)


            return jsonCatalogs

        } catch {
            print ("error")
            return nil
        }

I don't know why it doesn't work in Swift 4 with Xcode 9. Thank for your help ;-)

Er. Khatri · Accepted Answer · 2017-10-14 09:47:45Z

8

actually the thing is that your structs are wrong,

    fileprivate struct Catalog: Codable {
        var name: String
        var order: Int
        var products: [Products] // this key is wrong in your question, it should be products instead of product
    }

    //this particular structure was missing as your products is having a dictionary and in that dictionary you are having product at key product
    fileprivate struct Products: Codable {
        var product: Product
    }
    fileprivate struct Product: Codable {
        var title: String
        var reference: String
    }

now you can check your fucntion and also you can easily debug it using try catch with error handlings

...

// JSON Decoder

  do {
        let jsonData = try Data(contentsOf: URL(fileURLWithPath:filePath), options: .alwaysMapped)

        let jsonDecoder = JSONDecoder()

        let jsonCatalogs = try? jsonDecoder.decode(Array<Catalog>.self,from: jsonData)
        print(jsonCatalogs)
        return jsonCatalogs

    } catch let error {
        print ("error -> \(error)") // this will always give you the exact reason for which you are getting error
        return nil
    }

answered Oct 14, 2017 at 9:47

Er. Khatri

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2 Comments

Sébastien REMY Over a year ago

Thanks @Er. Khatri, ;-)

Er. Khatri Over a year ago

@iLandes if it works for you kindly accept the answer, kudos

Tejveer Sambariya · Accepted Answer · 2018-08-23 06:36:02Z

Try this solution according to your JSON and i have worked with Decoder in swift 4 with xcode 9.4.

    struct Catalog : Decodable {
        let name : String?
        let order : Int?
        let productArray : [Products]? // this is products array.
 }

    struct Products : Decodable {
        let productDict : Product? // this is product dictionary
 }
    struct Product : Decodable {
        let title : String?
        let reference : String? 
}
 var catalogArray = [Catalog]() // Declaration

    // JSON Decoder   
do {
            let jsonData = try Data(contentsOf: URL(fileURLWithPath:filePath), options: .alwaysMapped)
            let jsonDecoder = JSONDecoder()
            let jsonCatalogs = try? jsonDecoder.decode(Catalog.self,from: jsonData)
            return jsonCatalogs
        } catch let error {
            print ("error -> \(error)") // this will always give you the exact reason for which you are getting error
            return nil
        }

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