How to implicitly wrap a value that can be null or an array into an Scala Option

Question

I have this Java class in a Jar file included as a dependency of an Scala program (like the Axis jar): ``` class MyClass { private String[] someStrings; public String[] getSomeStrings() { return someStrings; } } ``` In my Scala program I have a Java API that return an instance of MyClass instance of MyClass to my program in Scala: ``` val myInstance = JavaAPI.getInstanceOfMyClass() ``` Then I try to use the someStrings array in my Scala program but it's null (let say that it wasn't properly initialized) ``` for(str <- myInstance.getSomeStrings()) ... ``` So this throws a NullPointerException. I've found that in order to use it in the for comprehension I can wrap it into an Option so that it handles the NPE properly. ``` for(str <- Option[Array[String]](myInstance.getSomeStrings).getOrElse(Array[String]()) ``` But that doesn't look OK to me. Is there a way to create like an implicit method that takes that value even if it's null and wrap it into the Option, like: ``` implicit def wrapN…

Accepted Answer

I don't think your version with `getOrElse` is that bad (you can make it a little shorter by removing the `[Array[String]]` after `Option`, since that can be inferred). If you want something even more concise, the following works:

```
for (str <- Option(myInstance.getSomeStrings).flatten) ...
```

You could also use the fact that `Option` has a `foreach`:

```
for {
  strings <- Option(myInstance.getSomeStrings)
  str <- strings
} ...
```

Note that you can't use `yield` here, for the reason that drexin highlights in a comment below.

Or you could pimp `MyClass`:

```
implicit def withNullWrapper(c: MyClass) = new {
  def getSomeStringsOrNot() = Option(c.getSomeStrings).getOrElse(Array[String]())
}

for (str <- myInstance.getSomeStringsOrNot) ...
```

How to implicitly wrap a value that can be null or an array into an Scala Option

Solution

Problem