Confusion in assigning form values for input type text

Question

Below are my Page and Spec. I am able to enter the value for firstName but I am getting the below error for lastName. I thought we can assign the value using '=' operator based on Geb doc here http://www.gebish.org/manual/current/navigator.html#text_inputs_and_textareas

geb.error.UnresolvablePropertyException: Unable to resolve lastName as a property to set on NewConsumerApplicationPage's Navigator context
    at geb.content.NavigableSupport.propertyMissing(NavigableSupport.groovy:141)
    at geb.Browser.propertyMissing(Browser.groovy:182)
    at geb.spock.GebSpec.propertyMissing(GebSpec.groovy:59)
    at WorkItemSpec.Create workitem(WorkItemSpec.groovy:32)

Page

class NewConsumerApplicationPage extends Page
{static content =
    {
        newApplicationForm
        { $("form", id: "newApplicationConsumerForm") }

        firstName
        {newApplicationForm.find("input", id: "newApplication_primaryApplicant:consumerIdentification:firstName")}

        lastName
        {newApplicationForm.find("input", id: "newApplication_primaryApplicant:consumerIdentification:lastName")}

        submitButton
        {
            $("button", id: "newConsumerApplication_submit")
        }
    }
}

Spec

def "Create workitem"()
{
    given : "I am successfully logged into the application"
    to NewConsumerApplicationPage

    when:
    firstName.value "CCERASTOSTIGMA"
    lastName = "PAULA"

    submitButton.click()

    then : 
    at ApplicationSummaryPage
}

Answer 1

I've got the answer from Geb mailing list. Posting it here for everyone's benefit.

That's a bit confusing, but this section of the manual is part of the "form control shortcuts", i.e. it only works on a form content element. Assuming your form has a name=lastName input element, this would work:

newApplicationForm.lastName = 'value'

It does not work however when manually selecting input elements of a form using $/find.