CODEWITHSUNDEEP
scalaplayframeworkplayframework-2.0
windweller
windweller

Reputation: 2385

Weird situation with Scala Play - type inference

@(css: Option[String])(content: Html)(customJS: Option[Array[String]])

 @for(js <- customJS if !customJS.isEmpty) {
            <script src="@routes.Assets.at(js)"></script>
        }

I was writing for this small for-comprehension that will loop through and print out the uri String. Since it is possible to be none, or an array of Strings, I used Option.

Then the complier from typesafe activator told me that @routes.Assets.at() is supposed to take a String not an Array[String]. I'm in shock because js is supposed to be String right?

Then I tried to write like this:

 @for(js <- customJS if !customJS.isEmpty) {
      @var uri = js
            <script src="@routes.Assets.at(js)"></script>
        }

Then the complier said that added line is illegal start of "simple expression".

It is not a simple expression! It is a full for-comprehension with {}! Also I was eventually forced to use js.asInstanceOf[String] to fool the complier. I'm not glad with this because once I was told that I should never use asInstanceOf. So what's wrong with my original code?

Upvotes: 1

Views: 73

Answers (1)

senia
senia

Reputation: 38045

Note that you should not use Array - use Seq.

There is no need in Option[Seq[String]] - use Seq[String]. Instead of None you could always use an empty Seq.

In case you still want to use Option[Seq[String]] you should rewrite your for like this:

@for(jsArray <- customJS; js <- jsArray) {
  <script src="@routes.Assets.at(js)"></script>
}

You don't need if !customJS.isEmpty. Option is something like collection with 1 or 0 elements. Element of Option[Array[String]] is Array[String].

Upvotes: 1

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