How I can reference a field defined in the gradle script?

I have a script to prepare build of an apk.

It defines some value which has some random specific for each build value:

def salt = generateSalt()

def generatedSalt() {
 return generateRandomlySalt
}

In the same script I want to have another method which will operate on this value.

def generateMapAndSalt() {
  // here is additional logic which depends on the defined salt
  generateEncodedHash(certificate, salt, shaKey)
}

There is another method inside of android closure which will pass this defined salt value to the buildConfigFiles. How do I reference once generated salt value from defined method? Tired accessing it with following syntax:

this.$salt
$salt
salt

With no luck.