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Mickael_Belhassen
Aug 2022

Hi,

My Realm model is also codable, and theses properties can be null, but when I get the JSON from the serve and decode it. It’s not working because he doesn’t know map the optional value

I need to implement the decoder method to solve this. I don’t want to implement decoder to all my realm model

There is an optional persisted propertyWrapper @OptionalPersisted something like this?

JayJason WootenCommunity Supporter
Aug 2022

Which properties? Can you include the Realm Model you’re referring to and perhaps a brief segment of the JSON you’re working with? Also, a snippet of the code you’ve attempted would be very helpful in clarifying the question

Mickael_Belhassen
Aug 2022

My model:

@objcMembers
class Supplier: Object, Coddle {
    @Persisted(primaryKey: true) var id: UUID =  UUID()
    @Persisted var name: String =  ""
    @Persisted var phoneNB: String?
    @Persisted var address: String?
    @Persisted var email: String?
    @Persisted var website: String?
    @Persisted var createdAt: Date = Date()

    convenience init(name: String, phoneNB: String?, address: String?, email: String?, website: String?) {
        self.init()
        self.name = name
        self.phoneNB = phoneNB
        self.address = address
        self.email = email
        self.website = website
    }
}

The JSON that I’m trying to parse

{
   "message":"OK",
   "data":[
      {
         "phoneNB":null,
         "faxNB":null,
         "address":null,
         "id":"477076BB-3114-4750-8E4F-042EF65B31E0",
         "website":null,
         "email":null,
         "createdAt":"2022-08-12T00:00:00Z",
         "name":"sup",
         "user":{
            "id":"661FC780-B01B-42E4-875A-C60A0B30EE34"
         }
      }
   ],
   "code":200
}

The error that I get
Decoded JSON error: valueNotFound(Swift.Optional<Swift.String>, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "data", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "phoneNB", intValue: nil)], debugDescription: "Expected Optional<String> but found null value instead.", underlyingError: nil))

It’s fail on phoneNB field. In my Realm model I marked it optional ?

Mickael_Belhassen
Aug 2022

To fix the error I need to implement manually the decoder method

    convenience required init(from decoder: Decoder) throws {
        self.init()
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decode(UUID.self, forKey: .id)
        name = try container.decode(String.self, forKey: .name)
        phoneNB = try container.decodeIfPresent(String.self, forKey: .phoneNB)
        address = try container.decodeIfPresent(String.self, forKey: .address)
        email = try container.decodeIfPresent(String.self, forKey: .email)
        website = try container.decodeIfPresent(String.self, forKey: .website)
        createdAt = try container.decode(Date.self, forKey: .createdAt)
    }

I don’t want to add the method manually, I want to let the compier to synthesize it

JayJason WootenCommunity Supporter
Aug 2022

Forgive the question but at first glance, the Realm object model Supplier doesn’t appear to match the presented JSON - the JSON data is a tier lower within a data child node. Perhaps there’s a third party library installed or more to it?

But the question is about the optional value so I simplified your json data just for testing with optionals to this:

let supplierJSONString = 

    {
       "phoneNB":null,
       "id":"477076BB-3114-4750-8E4F-042EF65B31E0",
       "name":"sup"
    }

and then created a Realm Model to map it to

class Supplier: Object, Codable {
    @Persisted(primaryKey: true) var id: UUID =  UUID()
    @Persisted var name: String =  ""
    @Persisted var phoneNB: String?
}

and then some quick code to encode the JSON string and then decode it into the Realm object

    let jsonData = self.supplierJSONString.data(using: .utf8)!
    let response = try! JSONDecoder().decode(Supplier.self, from: jsonData)
    
    print(response)

and printed to console

Supplier {
	id = 477076BB-3114-4750-8E4F-042EF65B31E0;
	name = sup;
	phoneNB = (null);
}

So it looks like the optional is being set to NULL as it should.

Perhaps a bit more clarity in the question and model would help us narrow the issue?

2 years later
JayJason WootenCommunity Supporter
Jul 2024

@Vishal_Deshai

No, a Realm List cannot be optional. But why would you want that. If it contains no elements then it’s just an empty list, right?

Also, this question is about 3 years old - it may be better to start a new topic/question with more details about what you’re attempting to do.


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