product.kt

class ProductObservable() : BaseObservable(){
constructor(weight : String?) : this() {
     this.weight = weight
}
@SerializedName("weight")
    @get:Bindable
    var weight: String? = null
        set(value) {
            field = value
            weightError = if (field.isNullOrEmpty() || (field
                    ?: "0.00").toDouble() == 0.00
            ) "Required*" else null
            notifyPropertyChanged(BR.weightError)
            notifyPropertyChanged(BR.weight)
        }
@get:Bindable
    var weightError: String? = null
        set(value) {
            field = value
            notifyPropertyChanged(BR.weightError)
        }
}