具有自定义setter Kotlin的非可选属性

Question

I hope someone can help, I am writing moving from java to Kotlin and I want to have a property that it initialised in the init block, that has a custom setter but is non optional.

Here is my code below, however this has a warning that tag must be initialised

I would like to make it lateInit, but that means it has to be optional (which I don't want)

class SkiMarker(mapView: MapView, tag:Tag) : Marker(mapView){
var tag:Tag      <- ERROR here
    set(tag){
        this.tag = tag
        if(tag != null){
            this.mPosition = GeoPoint(tag.lat,tag.lon)
        }
    }


init {
    this.tag            = tag
    this.mPosition      = GeoPoint(tag.lat,tag.lon)
    val window          = MyInfoWindow(mapView,tag)
    this.infoWindow     = window
    window.subject.observeOn(AndroidSchedulers.mainThread()).subscribe { it ->
        setIconForTracking(it)
    }
  } 
}

Many thanks in advance for any comments

Answer 1

For that logic you only need to use a backing field :

class SkiMarker(mapView: MapView, tag:Tag) : Marker(mapView) {
    var tag: Tag = tag
        set(newTag){
            field = newTag  // `field` is a keyword
        }
}

Note that code like set(newTag) {tag = newTag} is equivalent to setTag(newTag: Tag) { setTag(newTag) } where it is actually calling the setter from within itself in a recursion.

Also, tag is never null , so if(tag != null) is meaningless.