diff --git a/extensions/record.go b/extensions/record.go
index 7c7904e..5c8bc81 100644
--- a/extensions/record.go
+++ b/extensions/record.go
@@ -133,19 +133,42 @@ func (t *SexpRecord) MarshalJSON() ([]byte, error) {
 }
 
 func (t *SexpRecord) Explain(env *glisp.Environment, sym string, args []glisp.Sexp) (glisp.Sexp, error) {
-	if len(args) > 1 {
+	switch len(args) {
+	case 0:
+		return t.GetField(sym)
+	case 1:
+		return t.GetFieldDefault(sym, args[0]), nil
+	default:
 		return glisp.SexpNull, fmt.Errorf("record field accessor need not more than one argument but got %v", len(args))
 	}
-	if _, ok := t.class.fieldsMeta[sym]; !ok {
-		return glisp.SexpNull, fmt.Errorf("record<%s> not have a field named %s", t.TypeName(), string(sym))
-	}
-	fv, _ := t.value.HashGet(glisp.SexpStr(sym))
-	if len(args) == 1 && fv == glisp.SexpNull {
-		fv = args[0]
+}
+
+func (t *SexpRecord) GetField(name string) (glisp.Sexp, error) {
+	if _, ok := t.class.fieldsMeta[name]; !ok {
+		return glisp.SexpNull, fmt.Errorf("record<%s> not have a field named %s", t.TypeName(), name)
 	}
+	fv, _ := t.value.HashGet(glisp.SexpStr(name))
 	return fv, nil
 }
 
+func (t *SexpRecord) GetFieldDefault(name string, defaultVal glisp.Sexp) glisp.Sexp {
+	ret, err := t.GetField(name)
+	if err != nil || ret == glisp.SexpNull {
+		return defaultVal
+	}
+	return ret
+}
+
+func (t *SexpRecord) SetField(name string, val glisp.Sexp) error {
+	if f, ok := t.class.fieldsMeta[name]; ok {
+		if err := checkTypeMatched(f.Type, val); err != nil {
+			return err
+		}
+		return t.value.HashSet(glisp.SexpStr(f.Name), val)
+	}
+	return fmt.Errorf("field %s not found", name)
+}
+
 func IsRecord(args glisp.Sexp) bool {
 	_, ok := args.(*SexpRecord)
 	return ok
@@ -241,14 +264,7 @@ func AssocRecordField(name string) glisp.UserFunction {
 			return glisp.SexpNull, fmt.Errorf("second argument must be symbol but got %v", glisp.InspectType(args[1]))
 		}
 		record, field := args[0].(*SexpRecord), args[1].(glisp.SexpSymbol)
-		if f, ok := record.class.fieldsMeta[field.Name()]; ok {
-			if err := checkTypeMatched(f.Type, args[2]); err != nil {
-				return glisp.SexpNull, err
-			}
-			record.value.HashSet(glisp.SexpStr(f.Name), args[2])
-			return record, nil
-		}
-		return glisp.SexpNull, fmt.Errorf("field %s not found", field.Name())
+		return glisp.SexpNull, record.SetField(field.Name(), args[2])
 	}
 }
 
@@ -272,11 +288,15 @@ func CheckIsRecordOf(name string) glisp.UserFunction {
 		if !IsRecordClass(args[1]) {
 			return glisp.SexpNull, fmt.Errorf("second argument must be record class but got %s", glisp.InspectType(args[1]))
 		}
-		r, cls := args[0].(*SexpRecord), args[1].(SexpRecordClass)
-		return glisp.SexpBool(r.class.TypeName() == cls.TypeName()), nil
+		cls := args[1].(SexpRecordClass)
+		return glisp.SexpBool(IsRecordOf(args[0], cls.TypeName())), nil
 	}
 }
 
+func IsRecordOf(r glisp.Sexp, typ string) bool {
+	return IsRecord(r) && r.(*SexpRecord).class.TypeName() == typ
+}
+
 /* (defrecord MyType  (name type) (name2 type2) ) */
 func DefineRecord(name string) glisp.UserFunction {
 	return func(env *glisp.Environment, args []glisp.Sexp) (glisp.Sexp, error) {
@@ -397,3 +417,40 @@ func paddingRight(str string, max int) string {
 	}
 	return str
 }
+
+type RecordClassBuilder struct {
+	cls *sexpRecordClass
+}
+
+func NewRecordClassBuilder(className string) *RecordClassBuilder {
+	return &RecordClassBuilder{cls: &sexpRecordClass{typeName: className, fieldsMeta: make(map[string]sexpRecordField)}}
+}
+
+func (b *RecordClassBuilder) AddField(name string, typ string) *RecordClassBuilder {
+	if _, ok := b.cls.fieldsMeta[name]; ok {
+		return b
+	}
+	b.cls.fieldNames = append(b.cls.fieldNames, name)
+	b.cls.fieldsMeta[name] = sexpRecordField{Name: name, Type: typ}
+	return b
+}
+
+func (b *RecordClassBuilder) Build(env *glisp.Environment) SexpRecordClass {
+	env.Bind(b.cls.typeName, b.cls)
+	env.AddMacro(b.cls.constructorName(), func(_e *glisp.Environment, _args []glisp.Sexp) (glisp.Sexp, error) {
+		lb := glisp.NewListBuilder()
+		lb.Add(b.cls.getConstructor())
+		for i := range _args {
+			if i%2 == 0 {
+				lb.Add(glisp.MakeList([]glisp.Sexp{
+					_e.MakeSymbol("quote"),
+					_args[i],
+				}))
+			} else {
+				lb.Add(_args[i])
+			}
+		}
+		return lb.Get(), nil
+	})
+	return b.cls
+}
diff --git a/tests/glisp_test.go b/tests/glisp_test.go
index 1bc0f61..97c4f33 100644
--- a/tests/glisp_test.go
+++ b/tests/glisp_test.go
@@ -661,3 +661,14 @@ func TestListFuzzyMacroName(t *testing.T) {
 	testMacro(`(fuzzy-123)`, `number:123`)
 	testMacro(`(fuzzy-456)`, `number:456`)
 }
+
+func TestDefineClassInGolang(t *testing.T) {
+	vm := loadAllExtensions(glisp.New())
+	extensions.NewRecordClassBuilder("test/Options").
+		AddField("Name", "string").
+		AddField("Age", "int").
+		Build(vm)
+	script := `(def p (->test/Options Name "hello" Age (+ 1 2))) (assert (= "hello" (:Name p))) (assert (= 3 (:Age p)))`
+	_, err := vm.EvalString(script)
+	ExpectSuccess(t, err)
+}