Recreating the if/else in groovy: giving multiple closures arguments to a function

Question

While trying to reinvent the if/else syntax with closures in groovy, I couldn't manage to make it work. I think putting multiple closures outside the parenthesis is not permitted, but it could be something else.

If it isn't permitted, how would you reproduce the if/else syntax? This is a thought experiment, so don't tell me about the the inefficiency of this implementation.

My code:

void ifx(boolean condition, Closure action){
  ["${true.toString()}": action].get(condition.toString(), {})()
}

void ifx(boolean condition, Closure action, Closure elsex){
  ["${true.toString()}": action, "${false.toString()}": elsex].get(condition.toString())()
}

void elsex(Closure action){
    action()
}

ifx(1==2){
    println("1")
} ifx(1==3){
    println("2")
} elsex{
    println("3")
}

Error message:

java.lang.NullPointerException: Cannot invoke method ifx() on null object

Answer 1

Something along these lines works:

updated with closures to avoid global state:

def ifx( outerCondition, outerBlock ) {
  boolean matched = false
  def realIfx
  realIfx = { condition, block ->
    if (condition) {
      matched = true
      block()
    }
    [ifx: realIfx, elsex: { elseBlock -> if(!matched) elseBlock() }]
  }

  realIfx outerCondition, outerBlock
}

And some testing:

def result

ifx(1 == 2) {
  result = 1
} ifx(1 == 3) {
  result = 2
} elsex {
  result = 3
}

assert result == 3
result = null


ifx (1 == 2) {
  result = 1
} ifx (2 == 2) {
  result = 2
} elsex {
  result = 3
}

assert result == 2
result = null

ifx (true) {
  result = 1
} ifx (2 == 1) {
  result = 2
} elsex {
  result = 3
}

assert result == 1