adding objects in array creates duplicate values in swift

Question

I have an array of custom objects but when I add items to array it creates duplicate of last item add in array. Below is my code, please suggest where is the mistake, this small thing not able to get it.

var tempArr:[AnimalViewModel] =  [AnimalViewModel]()

        do {

            var objAnimal = Animal()

            var result = try managedContext.fetch(fetchRequest)
            for ds in result as! [NSManagedObject] {

            objAnimal.name = (ds.value(forKey: "name")) as! String
            objAnimal.type = (ds.value(forKey: “type”)) as! String

                Var objAVM = AnimalViewModel(aniModel: objAnimal)
                tempArr.append(objAVM)

            }
        } catch {
            print(" Error ")
        }

The array tempArr contains all duplicate element as last inserted element even objAnimal contains different values.

Thanks,

Create a new Animal each time inside the for loop. Even better is to have your fetch request return an array of your entity class and use that as a parameter when calling the AnimalViewModel constructor — Joakim Danielson
– Joakim Danielson, Commented Feb 7, 2019 at 17:35

vadian · Accepted Answer · 2019-02-07 17:47:18Z

First of all never print a meaningless literal string like "Error" in a catch block. Print always the error instance.

Animal is obviously a class (reference type). You are creating one instance and the properties are updated in the loop. As always the same instance is used the values are overwritten and you get result.count items with the same contents.

Create new instances inside the loop and replace Entity with the real entity name

var tempArr = [AnimalViewModel]()

do {
    let result = try managedContext.fetch(fetchRequest) as! [Entity] // let !
    for ds in result {

        let objAnimal = Animal()  // let !
        objAnimal.name = ds.name
        objAnimal.type = ds.type

        let objAVM = AnimalViewModel(aniModel: objAnimal)  // let !
        tempArr.append(objAVM)
    }
} catch {
    print(error)
}

And please notice and fix the warnings about never mutated variables

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