Kotlin primary and secondary constructor issue

Question

I have two constructors in my Kotlin object, a primary and a secondary. The primary has nothing in it and the secondary takes some parameters. I would like to map a DTO in the secondary constructor, but I don't see what is the problem.

Example

open class User(): RealmObject() {

    @PrimaryKey
    open var id: Long = 0

    open var login: String? = null

    open var firstName: String? = null

    open var surname: String? = null

    open var isAdmin: Boolean = false

    open var groups: RealmList<Int>? = null

    constructor(id: Long?, login: String?, firstName: String?, surname: String?, admin: Boolean?, groups: List<Int>?) : this()

    companion object {
        fun map(dto: UserDTO): User {
            Timber.d(dto.toString()) //The response data from the WS, OK with some data
            val groups = RealmList<Int>()
            dto.groups?.forEach { groups.add(it) }
            val u = User(dto.id, dto.login, dto.firstName, dto.surname, dto.admin, groups) //Calling the secondary constructor
            Timber.d(u.toString()) // Everything is null or false, KO
            return u
        }
    }
}

Submersed · Accepted Answer · 2017-11-09 04:19:58Z

1

A couple of things look a little off. You're calling your primary constructor's "this" with no arguments, and not setting the passed in values in the secondary either; since they aren't declared inline on the constructor as val or var so they won't stick around after the constructor finishes.

A better approach here would be to just use one constructor declare all your val/vars in the constructor rather than the class body, and provide default initialization values. This way, you can use named arguments for construction, which negates the need for multiple in this case.

Ex:

open class SomeClass(@PrimaryKey
                     open var id: Long = 0,
                     open var login: String? = null,
                     open var firstName: String? = null,
                     open var surname: String? = null,
                     open var isAdmin: Boolean = false,
                     open var groups: RealmList<Int>? = null): RealmObject()

edited Nov 9, 2017 at 4:19

answered Nov 7, 2017 at 16:41

Submersed

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1 Comment

Maurice Over a year ago

Thanks for the tip and the help.

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