Valid to add null to listOfNotNull()?-CodePudding

I've read following:

listOfNotNull(
    if (isSomeCondition) {
        ListSomeItem(123)
    } else null
)

Creating listOfNotNull() with a null in it? Is this valid?

CodePudding user response：

If your condition isSomeCondition is false the list will not insert the null value and it will be empty

Check this example

val list = listOfNotNull(null)
print(list.size)

The output will be zero

And in this example

val list = listOfNotNull(null, null, 1, null)
print(list.size)

Only 1 will be inserted and the size will be 1

Basically, listOfNotNull will filter the values and create a list from the non nulls values

The source code of listOfNotNull

public fun <T : Any> listOfNotNull(vararg elements: T?): List<T> = elements.filterNotNull()

So your code will be like insert or be empty