Write in parcer nullable value in kotlin

Question

Backend returns nullable Int? How should I write nullable value?

 date class Foo (var value: Int?){
   constructor(source: Parcel) : this(
     source.readInt()
   )

   override fun writeToParcel(dest: Parcel, flags: Int) {
     dest.writeInt(value) // doesn't compile - writeInt expect no null value
   }
 }

Now I got solution:

dest.writeInt(value?: -1)

And then check to -1

or write Int like string and then use value of...

but I think it's ugly and wrong.

RESOLVED! My answer:

source.readValue(Int::class.java.classLoader) as Int?,
dest.writeValue(value)

Answer 1

Resolved by:

source.readValue(Int::class.java.classLoader) as Int?,
dest.writeValue(value)

Answer 2

This largely depends on what is the semantics of null as a value of your nullable property. It can mean:

• If value is null then it is absent and should not be written at all:

  value?.let { writeInt(it) }
  

  Of course, the Parcel receiver should be able to determine if it should read the value or not, this should be clear from the values written earlier.

• value is provided by some code, and it is an error if it is null at the point where it should be written:

  check(value != null) { "value should be not null at the point it's wriiten" }
  writeInt(value!!)
  

  Also, in this case, consider using lateinit var instead of nullable property.

• Some default value should be used instead of value:

  writeInt(value ?: someDefaultValue())
  

  With Parcel, this does make sense, because otherwise, if the value is missing, you have to specify the fact somewhere else.

• ... (null can actually mean many things)

Also, this answer shows many idiomatic ways of dealing with nullable values, and you might find some of them useful.