Question

I’m provided a library with a builder function using default/named params. Something like

def builder = new {
    def apply(
      a:Int = 0,
      b:Int = 0,
      c:Int = 0):String = {
       "a="+a+", b="+b+", c="+c
      }
}

I need to consume a Mapped Collection of parameters (http query params) and call the builder properly. I can brute force it with repetitive code but there must be a better “functional” way to do this. Below is my rather poor attempt. As you can see it overrides the builder’s default params. Please show me the light!

val inParams = Map("a" -> 1, "b" -> 2, "c" -> 3) //3 params passed in

builder(
  in.get("a").getOrElse(0),
  in.get("b").getOrElse(0),
  in.get("c").getOrElse(0)
)

val inParams = Map("a" -> 1, "c" -> 3) //2 params, out of sequence
builder(
  in.get("a").getOrElse(0),
  in.get("b").getOrElse(0),
  in.get("c").getOrElse(0)
)

Answer 1

Map has a getOrElse method.

val in = Map("a" -> 1, "c" -> 3) //2 params, out of sequence
builder(
  in.getOrElse("a", 0),
  in.getOrElse("b", 0),
  in.getOrElse("c", 0)
)

Or you can also do:

val in = Map("a" -> 1, "c" -> 3).withDefaultValue(0)
builder(in("a"), in("b"), in("c"))