Kotlin data classes JSON Deserialization - kotlin

Question

I am trying convert ApiEmployee to Employee and have written a test around it. I am confused about nulls in Kotlin as I am new to it.
ApiEmployee would be used for JSON conversion so it can have missing name field or or empty or can come as null. In that case, I don't want to add into list and safely ignore it.
I am getting Method threw 'kotlin.KotlinNullPointerException at exception. at apiEmployee.name!!.isNotBlank()
ApiEmployee
data class ApiEmployee(val image: String? = "image",
val name: String? = "name test",
val description: String? = "",
val id: String? = "")
Employee
data class Employee(val imagePath: String, val id: String)
EmployeeConverter(converts ApiEmployee to Employee)
fun apply(apiEmployees: List<ApiEmployee>): List<Employee> {
val employees = mutableListOf<Employee>()
for (apiEmployee in apiEmployees) {
if (apiEmployee.name!!.isNotBlank()){
employees.add(Employee(apiEmployee.image!!, apiEmployee.id!!)
}
}
}
EmployeeConverterTest
#Test
fun `should not add employee without name into employee list`() {
val invalidApiEmployee = ApiEmployee("image", null, "description", "id")
val convertedEmployees : List< Employee > = employeeConverter.apply(listOf( invalidApiEmployee))
assertThat(convertedEmployees.size).isEqualTo(0)
}

Answer 1

What you want to do is check if the name is null first and then if it is empty.
val employeeNameIsNotEmpty = apiEmployee.name?.isNotBlank() ?: false
if (employeeNameIsNotEmpty) {
// do stuff
}
The apiEmployee.name?.isNotBlank() will run and return a value only if name is not null. If name is null then the statment on the right side of ?: will return its value, which in this case should be false.
In this case however Kotlin has already put this particular example into an extension function
.isNullOrBlank()
So you could change it to:
if (!apiEmployee.name.isNullOrBlank()) {
// do stuff
}
As a side note you really don't whant to do this Employee(apiEmployee.image!!, apiEmployee.id!!).
Because image and id could still be null and crash your code with the same error.

Answer 2

Either pass the value for name.
ApiEmployee("image", "name", "description", "id")
(or)
Change the if condition as mentioned below (with ? operator):-
if (apiEmployee.name?.isNotBlank()){
?. performs a safe call (calls a method or accesses a property if the
receiver is non-null)
!! asserts that an expression is
non-null
The code asserts that name is not null and checking for not blank.
Probably, I think you are trying to do null and not blank check. You can use ? operator (safe call) for that. This means isNotBlank() gets executed only if the name is not null.