func (f *FieldHandler) StringSelector() string {
	return f.selector
}
StringSelector returns the field selector of string type.
package tagexpr
import "reflect"
type FieldHandler struct {
	selector string
	field    *fieldVM
	expr     *TagExpr
}
func newFieldHandler(expr *TagExpr, fieldSelector string, field *fieldVM) *FieldHandler {
	return &FieldHandler{
		selector: fieldSelector,
		field:    field,
		expr:     expr,
	}
}