Clear a Field using ScriptRunner

[SMAtlassianMber]

I have added the following Behaviour, but I also need to make sure the Fixed Deadline Date field is cleared if the Fixed Deadline is No. Would I need to add something like this to last line in else 

issue.setCustomFieldValue(fxieddeadlinedateField, null)

def fixeddeadlineField = getFieldByName("Fixed Deadline")
def fixeddeadlinedateField = getFieldByName("Fixed Deadline Date")

if (fixeddeadlineField.value.toString() == "Yes") {
fixeddeadlinedateField.setRequired(true)
fixeddeadlinedateField.setHidden(false)
}
else {
fixeddeadlinedateField.setRequired(false)
fixeddeadlinedateField.setHidden(true)
}

[SMAtlassianMber]

I got this to work.

def fixeddeadlineField = getFieldByName("Fixed Deadline")
def fixeddeadlinedateField = getFieldByName("Fixed Deadline Date")
def defaultValue = null

if (fixeddeadlineField.value.toString() == "Yes") {
fixeddeadlinedateField.setRequired(true)
fixeddeadlinedateField.setHidden(false)
}
else {
fixeddeadlinedateField.setRequired(false)
fixeddeadlinedateField.setHidden(true)
fixeddeadlinedateField.setFormValue(defaultValue)
}

[Steven F Behnke]

The documentation states that there is a 'setFieldValue("")' method -- You should be able to pass in a Blank String or a null.

[SMAtlassianMber]

When i try the following, I get the variable "issue" is undeclared 

def fixeddeadlineField = getFieldByName("Fixed Deadline")
def fixeddeadlinedateField = getFieldByName("Fixed Deadline Date")

if (fixeddeadlineField.value.toString() == "Yes") {
fixeddeadlinedateField.setRequired(true)
fixeddeadlinedateField.setHidden(false)
}
else {
fixeddeadlinedateField.setRequired(false)
fixeddeadlinedateField.setHidden(true)
issue.setCustomFieldValue(fixeddeadlinedateField, null)
}