What's the idiomatic way to map a nullable list? ...

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[Pablo]

What's the idiomatic way to map a nullable list?

Let's say I have this class

class ProductModel {
   val productListModel: List<ProductListModel>? = null,
}

And I have the mapper like this

fun map(input : ProductModel) : List<Product>{
  return input.productListModel?.map{Product(....)}.orEmpty()
}

Is there another elegant way? If the list is null or empty I should return an empty List of Product and if not, the list mapped

[tddmonkey]

In your model, why would you allow a nullable list? The default can just be an emptyList() and avoid the whole issue

[Rob Elliot]

If productListModel has to be nullable for some reason, then you can save yourself one character by doing input.productListModel.orEmpty().map{Product(....)}

[Joan Colmenero]

@Rob Elliot but then even if the list is empty it will try to map, right?

[Rob Elliot]

Hmm - interesting, I’d assumed List<T>.map would have an if empty return this or perhaps an if empty return emptyList(), which always returns the same object, as an optimisation. But looks like it instantiates a new list instance regardless. Generally I prefer to get away from null as soon as possible, but perhaps in this case that’s bad advice.

[Pablo]

Yes, I did it like this because I thought that checking the null or empty it will avoid the map