Realm-cocoa: List property is not being saved

[ankushkushwaha]

Goals

Save an Object which has 2 properties Date and List (Array).

Expected Results

The object should be saved in database with both property values i.e. date and List

Actual Results

The object get saved but only with one property, which is of type Date. The List property is not being saved in database.

Steps to Reproduce

Code Sample

class _ElectricityPricesModel: Object { // Object class to save

    @objc dynamic var updated : Date?
    var data = List<_PriceModel>()
}


class ElectricityPricesModel: _ElectricityPricesModel { // class responsible to save the data

    static func savedElectricityPricesModel(realm: Realm?) -> ElectricityPricesModel! // app can only have one _ElectricityPricesModel 
    {
        if realm  == nil
        {
            return nil
        }

        let electricityPricesModel =  realm?.objects(ElectricityPricesModel.self)

        if electricityPricesModel?.first != nil
        {
            return electricityPricesModel?.first
        }

        let newElectricityPricesModel = ElectricityPricesModel()

        try! realm?.write {
            return realm?.add(newElectricityPricesModel)
        }

        return newElectricityPricesModel
    }

    static func updateIn(realm: Realm?, electricityPricesModel: EditableElectricityPricesModel?)
    {
        if electricityPricesModel == nil || realm == nil
        {
            return
        }

        let savedElectricityPricesModel = self.savedElectricityPricesModel(realm: realm)

        try! realm?.write {

            savedElectricityPricesModel?.data = electricityPricesModel!.data
            savedElectricityPricesModel?.updated = electricityPricesModel!.updated

        }
    }

}

I call the function as follows:

ElectricityPricesModel.updateIn(realm: self.realmObject, electricityPricesModel: electricityPricesModel)

And in next cycle (when I try to save the object again) I check the value by using breakpoint ans it shows the following result:

Printing description of savedElectricityPricesModel:
▿ Optional<ElectricityPricesModel>
  - some : ElectricityPricesModel {
    updated = 2017-12-11 14:00:00 +0000;
    data = RLMArray<_PriceModel> <0x1095347e0> (

    );
}

Version of Realm and Tooling

Realm framework version: 3.0.2

Realm Object Server version: ? --

Xcode version: 9.2

iOS/OSX version: 11.1.2

Dependency manager + version: COCOAPODS: 1.3.1

[bdash]

The declaration of your List<T> property should use let instead of var.

let data = List<_PriceModel>()

The compiler will now catch places where you attempt to assign to the data property rather than mutating it in place. This is necessary because Swift does not provide any means to intercept an assignment to a property whose type uses generics (more specifically, any type that is not representable in Objective-C).

For instance:

savedElectricityPricesModel?.data = electricityPricesModel!.data

Should instead be:

savedElectricityPricesModel?.replaceSubrange(0..<savedElectricityPricesModel.count, with: electricityPricesModel!.data)

[kalrashubham49]

I am still unclear about the solution, even after using let i am not getting my data persisted..

[ankushkushwaha]

@kalrashubham49 What is your issue? Please explain in detail.

[kalrashubham49]

List Type in not getting persisted in Realm. While all other properties are getting saved.

[ankushkushwaha]

Can you please paste some small a related code here?

[kalrashubham49]

class _ElectricityPricesModel: Object,Mappable { // Object class to save

    @objc dynamic var updated : Date?
    let data = List<_PriceModel>()

func mapping(map: Map)
    {
        updated <- map[“updated_at”]
        data <- map[“models”]
    }
}

class ElectricityPricesModel: _ElectricityPricesModel { // class responsible to save the data

    static func savedElectricityPricesModel(realm: Realm?) -> ElectricityPricesModel! // app can only have one _ElectricityPricesModel 
    {
        if realm  == nil
        {
            return nil
        }

        let electricityPricesModel =  realm?.objects(ElectricityPricesModel.self)

        if electricityPricesModel?.first != nil
        {
            return electricityPricesModel?.first
        }

        let newElectricityPricesModel = ElectricityPricesModel()

        try! realm?.write {
            return realm?.add(newElectricityPricesModel)
        }

        return newElectricityPricesModel
    }

    static func updateIn(realm: Realm?, electricityPricesModel: EditableElectricityPricesModel?)
    {
        if electricityPricesModel == nil || realm == nil
        {
            return
        }

        let savedElectricityPricesModel = self.savedElectricityPricesModel(realm: realm)

        try! realm?.write {

            savedElectricityPricesModel?.data = electricityPricesModel!.data
            savedElectricityPricesModel?.updated = electricityPricesModel!.updated

        }
    }

}

My Model is

[ankushkushwaha]

Okay @kalrashubham49

replace savedElectricityPricesModel?.data = electricityPricesModel!.data

with -

```
for priceModel in electricityPricesModel!.data
{
savedElectricityPricesModel?.data.append(priceModel)
}

```
Let me know if you face any problem.

[kalrashubham49]

Still not working. for Transforming List, i have used 2 methods both of
them are ot working

1 - overloading Operation <-

func <- (left: List, right: Map)

{

var array: [T]?



if right.mappingType == .toJSON {

    array = Array(left)

}



array <- right



if right.mappingType == .fromJSON {

    if let theArray = array {

        left.append(objectsIn: theArray)

    }

}

}

2 - Transforming List from Array

class RealmListTransform : TransformType where T:Mappable {

typealias Object = List<T>

typealias JSON = [[String:Any]]



let mapper = Mapper<T>()



func transformFromJSON(_ value: Any?) -> List<T>? {

    let result = List<T>()

    if let tempArr = value as? [Any] {

        for entry in tempArr {

            let mapper = Mapper<T>()

            let model : T = mapper.map(JSONObject: entry)!

            result.append(model)

        }

    }

    return result

}



func transformToJSON(_ value: Object?) -> JSON? {

    var results = [[String:Any]]()

    if let value = value {

        for obj in value {

            let json = mapper.toJSON(obj)

            results.append(json)

        }

    }

    return results

}

}

On Fri, Jun 1, 2018 at 6:48 PM, Ankush Kushwaha [e-mail]
wrote:

Okay @kalrashubham49 https://github.com/kalrashubham49

replace savedElectricityPricesModel?.data = electricityPricesModel!.data

with -
for priceModel in electricityPricesModel!.data
{
savedElectricityPricesModel?.data.append(priceModel)
}

Let me know if you face any problem.

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[colinmackey]

I am having this issue, my list property does not show up in my Realm when I inspect it with Realm Studio. It is declared using 'let' as @bdash has said. @kalrashubham49 did you find a solution to your problem? Using XCode 11.2.1 and Realm Swift 3.21.0.