Programming Groovy 2

19.9 The Parentheses Limitation and a Workaround

Let’s leave the pizza example behind and look at a simple register. This section will show how to create a DSL for a simple register, the device that lets us total amounts. Here is the first attempt to create that:

value = 0
def clear() { value = 0 }
def add(number) { value += number }
def total() { println "Total is $value" }

clear()
add 2
add 5
add 7
total()

The output from the previous code is as follows:

Total is 14

In this code, we wrote ​total​ and ​clear​ instead of ​total​ and ​clear​, respectively. Let’s drop the parentheses and try to call ​total​:

try {
  total
} catch(Exception ex) {
  println ex