Create and fill a 2D Array in Scala

Question

I have just started looking into Scala, and I decided to make a roguelike to get my feet wet. I come from a Java background, and I am having trouble working with the Scala Arrays.

When I try to make a level, what I call a room, I picture a two dimensional array with # as walls. I try to use, as I understand it, a Scala nested for-loop to place the # wall characters when i || j are 0, or when i || j is at the end of the array. Inside the braces of the for-loop, I have temp(i, j) = '#' which is giving me the error "Expression of type Char doesn't conform to expected type, Nothing" in my IDE, IntelliJ.

I have posted my code below, and if you could help me format and/or work with my Array correctly, that would be great.

class Room
{
    val room = generate

    def generate: Array[Char] =
    {
        var temp = Array[Char](10, 10)

        for (i: Int <- 0 to temp.length; j: Int <- 0 to temp.length)
        {
            if (i == 0 || j == 0 || i == temp.length-1 || j == temp.length-1)
                temp(i, j) = '#'
        }

        return temp
    }

    def print: Unit =
    {
        for (i <- 0 to 10)
        {
            var line: String = ""
            for (j <- 0 to 10)
            {
                line += room(i, j)
            }
            println(line)
        }
    }
}

Answer 1

var temp = Array[Char](10, 10) creates a 1-dimension Array containing two linefeed characters (10 being its value in ascii).

You'll want to use var temp = Array.ofDim[Char](10,10) instead. You can then access a cell using temp(i)(j) (and not temp(i, j)).

Also note that for (i <- 0 to 10) {} will cause an ArrayIndexOutOfBoundsException. You'll want to use for (i <- 0 until 10) {} instead.

---

You could also use the Array.tabulate method :

// Dummy implementation
scala> def calculateCellValue(i: Int, j: Int) = 
            if (i == 0 || j == 0 || i == 9 || j == 9)  '#' else 'x'

scala> val temp = Array.tabulate(10,10)(calculateCellValue)
temp: Array[Array[Char]] = Array(Array(#, #, #, #, #, #, #, #, #, #),
                                 Array(#, x, x, x, x, x, x, x, x, #),
                                 Array(#, x, x, x, x, x, x, x, x, #),
                                 Array(#, x, x, x, x, x, x, x, x, #),
                                 Array(#, x, x, x, x, x, x, x, x, #), 
                                 Array(#, x, x, x, x, x, x, x, x, #), 
                                 Array(#, x, x, x, x, x, x, x, x, #), 
                                 Array(#, x, x, x, x, x, x, x, x, #), 
                                 Array(#, x, x, x, x, x, x, x, x, #), 
                                 Array(#, #, #, #, #, #, #, #, #, #))