[1.2.0] [Kotlin] Having TWO ToOne<> relations in one Entity Class. - cannot read back second one.

Issue Basics

• ObjectBox version (are using the latest version?): 1.2.0
• Reproducibility: always

Reproducing the bug

Description

If I have an entity with 2 ToOne<> relation fields, one of these fields is not retrieved while reading from boxstore.

@Entity
data class EntityWord(
        @Id var id: Long = 0,
        var wordId: Int? = 0,
        var annotationDetails: ToOne<EntityAnnotation>? = null,
        var lineNo: Int? = 0,
        var wordNo: Int? = 0,
        var audioStart: String? = null,
        var audioEnd: String? = null,
        var mistakes: ToOne<EntityMistakes>? = null
)

EntityAnnotiation is an entity with primitive fields. EntityMistakes is further an Entity with 3 ToMany<> relations.

In this entity, I can retrieve annotationDetails but never mistakes.

I commented annotationDetails just to check, and THEN I can retrieve mistakes.

I’ve used the ObjectBox viewer to verify that the mistakes data does in fact exist in the boxstore.

I cant for the life of me figure out what am i missing in this. Surely, an Entity should be able to support more than ONE ToOne<> relations.

[greenrobot-team]

Trying to reproduce.

Found cause: relation fields inside a data class constructor break the ObjectBox initialization magic. Kotlin byte-code overwrites the values set by ObjectBox.

Background: the transformer adds the relation field initialization code right before any other statements in the constructor body, right after the super() call. However, Kotlin byte-code for data classes sets all fields again to the values provided through the constructor params.

So

@Entity
data class Example(
    @Id var id: Long = 0,
    val toOne: ToOne<Example>? = null
)

will actually turn into something behaving like:

public Example() {
  this(0L, null);
}

public Example(long id, @Nullable ToOne toOne) {
  this.toOne = new ToOne(this, Example_.toOne); // <-- ObjectBox transformer adds this
  this.id = id;
  this.toOne = toOne;
}

To work around this, specify relation fields as properties instead:

@Entity
data class Example(@Id var id: Long = 0) {
    lateinit var toOne: ToOne<Example>
}

This should also prevent side-effects when ObjectBox tries to build a data class with box data. -ut

[KishoreBabuIN]

Hey Markus Let me isolate the problem into a smaller kotlin project and send you a link.

I’ll need time till tomorrow… I’ve been away from work and travelling.

Cheers!

On 06-Nov-2017, at 6:48 PM, Markus Junginger [e-mail] wrote:

@barykaed https://github.com/barykaed Any updates? We have cases like you have and it works for us. We need to reproduce it in order to fix it… 😉

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