add a new x/sqlx sub-package and example

x/sqlx/struct_row.go

@@ -0,0 +1,92 @@
+package sqlx
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/kataras/iris/v12/x/reflex"
+)
+
+// DefaultTag is the default struct field tag.
+var DefaultTag = "db"
+
+type ColumnNameFunc = func(string) string
+
+func convertStructToColumns(typ reflect.Type, nameFunc ColumnNameFunc) (map[string]*Column, error) {
+	if kind := typ.Kind(); kind != reflect.Struct {
+		return nil, fmt.Errorf("convert struct: invalid type: expected a struct value but got: %q", kind.String())
+	}
+
+	// Retrieve only fields valid for database.
+	fields := reflex.LookupFields(typ, "")
+
+	columns := make(map[string]*Column, len(fields))
+	for i, field := range fields {
+		column, ok, err := convertStructFieldToColumn(field, DefaultTag, nameFunc)
+		if !ok {
+			continue
+		}
+
+		if err != nil {
+			return nil, fmt.Errorf("convert struct: field name: %q: %w", field.Name, err)
+		}
+
+		column.Index = i
+		columns[column.Name] = column
+	}
+
+	return columns, nil
+}
+
+func convertStructFieldToColumn(field reflect.StructField, optionalTag string, nameFunc ColumnNameFunc) (*Column, bool, error) {
+	c := &Column{
+		Name:       nameFunc(field.Name),
+		FieldIndex: field.Index,
+	}
+
+	fieldTag, ok := field.Tag.Lookup(optionalTag)
+	if ok {
+		if fieldTag == "-" {
+			return nil, false, nil
+		}
+
+		if err := parseOptions(fieldTag, c); err != nil {
+			return nil, false, err
+		}
+	}
+
+	return c, true, nil
+}
+
+func parseOptions(fieldTag string, c *Column) error {
+	options := strings.Split(fieldTag, ",")
+	for _, opt := range options {
+		if opt == "" {
+			continue // skip empty.
+		}
+
+		var key, value string
+
+		kv := strings.Split(opt, "=") // When more options come to play.
+		switch len(kv) {
+		case 2:
+			key = kv[0]
+			value = kv[1]
+		case 1:
+			c.Name = kv[0]
+			return nil
+		default:
+			return fmt.Errorf("option: %s: expected key value separated by '='", opt)
+		}
+
+		switch key {
+		case "name":
+			c.Name = value
+		default:
+			return fmt.Errorf("unexpected tag option: %s", key)
+		}
+	}
+
+	return nil
+}