Understanding Gradle dynamic tasks

Question

I'm reading about dynamic tasks in gradle and want to understand the syntax and meaning of the following code:

4.times { counter ->
    task "task$counter" << {
        println "I'm task number $counter"
    }
}
task0.dependsOn task2, task3

1. What does 4.times mean? Why 4?
2. What does -> mean? Now I understand it as a way to pass a parameter to a task. I'm sure its correct strictly speaking about groovy.

Answer 1

1. 4 is just a random value, you can pick 10 or 15 as well. This value is just used to create multiple tasks. Under the hood this method is invoked for times - think of it as if it was an iterator.

2. -> is used to indicate a closure param name. Without it, it would look like this:

   4.times { 
      task "task$it" << {
         println "I'm task number $counter"
      }
   }
   task0.dependsOn task2, task3
   

   Since it is default closure param name. If multiples closures are used (as in the example - for times and for adding an action), it's good practice to use dedicated names for closures. Here are the docs about closures.

Answer 2

Gradle based on Groovy and you can programming in gradle like in groovy or java. For your questions:

1. Look this http://mrhaki.blogspot.de/2009/09/groovy-goodness-looping-in-different.html

2. Look this http://www.groovy-lang.org/closures.html