...
Get fields will return each fieldname defined for the record as an array, except for special internal field names.
Example
$fields = getFields(in) // ["foo", "bah", "field3"]
$field = $fields[0] // $field = "foo"
$value - in.$field // equivalent to in.foo
The getFields function will return a list of field names. These can be extracted using normal array functions and assigned to a variable.
The dot notation supports dynamic access to fields when variables are used within the expression, in this case $field = "foo" so in.foo will be assigned to $value.