Using groovy.transform.Field to define another Field

Question

I am writing a Groovy script, where I need to use some of my fields inside closures. Below is a very simplified example to demonstrate my problem.

#!/usr/bin/env groovy

import groovy.transform.Field

@Field def first = 'one'
assert first == 'one'

So far so good. In my real-world case, this will hold a String representing a server name. I then modify this "default" value from command-line options - using CliBuilder() - maybe something like:

first = 'two'
assert first == 'two'

This still works. I now need to create a new field, from the one above:

@Field def second = first
assert second == 'two'

In my real-world case, this will be an HTTPBuilder() that I will be making REST calls with.

This fails:

Assertion failed: 

assert second == 'two'
       |      |
       'one'  false

Is there a way to get this to work?

A failed attempt to somehow work around this. Using an intermediary, something like:

def intermediary = first
assert intermediary == 'two'
@Field def second = intermediary

Fails with:

Caught: java.lang.reflect.InvocationTargetException
java.lang.reflect.InvocationTargetException
    at something.main(something)
Caused by: groovy.lang.MissingPropertyException: No such property: intermediary for class: something
    at something.<init>(something)
    ... 1 more

Answer 1

the annotation @Field declares member of the script class and any other script commands will go to script.run() method

for example the script

import groovy.transform.Field

@Field def first = 'one'
first = 'two'
@Field def second = first
assert second == 'two' // <<<---- fails because second=='one'

will be transformed approximately to this class during script compilation:

class scriptXXXX{
    Object first
    Object second
    
    scriptXXXX(){ // constructor
        first = 'one'
        second = first
    }

    void run(){ // script body
        first = 'two'
        assert second == 'two' : null    
    }
}

You could see this in groovyconsole by pressing Ctrl+T

---

as a variant you could separate field declaration and initialization:

@Field def first = 'one'
@Field def second
first = 'two'
second = first
assert second == 'two'