groovy.transform

## Annotation Type BaseScript

    @Documented
     @Retention(value=SOURCE)
     @Target(value={LOCAL_VARIABLE,PACKAGE,TYPE})
    public @interface BaseScript

Variable annotation used for changing the base script class of the current script.

The type of the variable annotated with `@BaseScript` must extend `Script`. It will be used as the base script class. The annotated variable will become shortcut to `this` object. Using this annotation will override base script set by Groovy compiler or `CompilerConfiguration` of `GroovyShell` Example usage:

     abstract class CustomScript extends Script {
         int getTheMeaningOfLife() { 42 }
     }

     @BaseScript CustomScript baseScript

     assert baseScript == this
     assert theMeaningOfLife == 42
     assert theMeaningOfLife == baseScript.theMeaningOfLife

In this example, the base script of the current script will be changed to `CustomScript` allowing usage of `getTheMeaningOfLife()` method. `baseScript` variable will become typed shortcut for `this` object which enables better IDE support.

The custom base script may implement the run() method and specify a different method name to be used for the script body by declaring a single abstract method. For example:

     abstract class CustomScriptBodyMethod extends Script {
         abstract def runScript()
         def preRun() { println "preRunning" }
         def postRun() { println "postRunning" }
         def run() {
             preRun()
             try {
                 3.times { runScript() }
             } finally {
                 postRun()
             }
         }
     }

      @BaseScript CustomScriptBodyMethod baseScript
     println "Script body run"

That will produce the following output:

     preRunning
     Script body run
     Script body run
     Script body run
     postRunning

Note that while you can declare arguments for the script body's method, as the AST is currently implemented they are not accessible in the script body code.

More examples:

     // Simple Car class to save state and distance.
     class Car {
         String state
         Long distance = 0
     }

     // Custom Script with methods that change the Car's state.
     // The Car object is passed via the binding.
     abstract class CarScript extends Script {
         def start() {
             this.binding.car.state = 'started'
         }

         def stop() {
             this.binding.car.state = 'stopped'
         }

         def drive(distance) {
             this.binding.car.distance += distance
         }
     }

     // Define Car object here, so we can use it in assertions later on.
     def car = new Car()
     // Add to script binding (CarScript references this.binding.car).
     def binding = new Binding(car: car)

     // Configure the GroovyShell.
     def shell = new GroovyShell(this.class.classLoader, binding)

     // Simple DSL to start, drive and stop the car.
     // The methods are defined in the CarScript class.
     def carDsl = '''
     start()
     drive 20
     stop()
     '''

     // Run DSL script.
     shell.evaluate """
     // Use BaseScript annotation to set script
     // for evaluating the DSL.
     @groovy.transform.BaseScript CarScript carScript

     $carDsl
     """

     // Checks to see that Car object has changed.
     assert car.distance == 20
     assert car.state == 'stopped'

Since:
  2.2.0
Author:
  Paul King, Vladimir Orany, Jim White

### Optional Element Summary

Optional Elements
`java.lang.Class` `value`

### Element Detail

#### value

    public abstract java.lang.Class value

Default:
  groovy.lang.Script.class