/*
This method evaluates the Field using the first and second value
and returns the result value. If the second operand type is a
missing return a missing value. If it is a string, and the
field is case insensitive, then convert the second operand to
lower case, range through the fields of the first and compare,
each field with the second. When equal, return the value. If
the field is case sensitive, use the Field method to directly
access the field and return it. For all other types, if the
first operand expression is missing, return missing, else return
null.
*/
func (this *Field) Apply(context Context, first, second value.Value) (value.Value, error) {
switch second.Type() {
case value.STRING:
s := second.Actual().(string)
v, ok := first.Field(s)
if !ok && this.caseInsensitive {
s = strings.ToLower(s)
fields := first.Fields()
for f, val := range fields {
if s == strings.ToLower(f) {
return value.NewValue(val), nil
}
}
}
return v, nil
case value.MISSING:
return value.MISSING_VALUE, nil
default:
if first.Type() == value.MISSING {
return value.MISSING_VALUE, nil
} else {
return value.NULL_VALUE, nil
}
}
}