feat: add handling for the interface field, when an Interface field is an object that has already been instantiated, use the type of the instantiated object itself instead of interface{}.

schema/schema.go

@@ -115,7 +115,6 @@ func ParseWithSpecialTableName(dest interface{}, cacheStore *sync.Map, namer Nam
 		value = reflect.New(value.Type().Elem())
 	}
 
-	modelValue := reflect.Indirect(value)
 	modelType := reflect.Indirect(value).Type()
 
 	if modelType.Kind() == reflect.Interface {
@@ -150,6 +149,7 @@ func ParseWithSpecialTableName(dest interface{}, cacheStore *sync.Map, namer Nam
 		return s, s.err
 	}
 
+	modelValue := reflect.New(modelType)
 	tableName := namer.TableName(modelType.Name())
 	if tabler, ok := modelValue.Interface().(Tabler); ok {
 		tableName = tabler.TableName()
@@ -166,7 +166,7 @@ func ParseWithSpecialTableName(dest interface{}, cacheStore *sync.Map, namer Nam
 
 	schema := &Schema{
 		Name:             modelType.Name(),
-		ModelValue:       modelValue,
+		ModelValue:       reflect.Indirect(value),
 		ModelType:        modelType,
 		Table:            tableName,
 		FieldsByName:     map[string]*Field{},

tests/interface_test.go

@@ -0,0 +1,23 @@
+package tests_test
+
+import (
+	"testing"
+
+	"gorm.io/gorm/utils/tests"
+	. "gorm.io/gorm/utils/tests"
+)
+
+func TestInterface(t *testing.T) {
+	vehicleWrite := &tests.Vehicle{Meta: &tests.MotorMeta{Power: "electric"}}
+
+	if err := DB.Create(vehicleWrite).Error; err != nil {
+		t.Fatalf("fail to create region %v", err)
+	}
+
+	vehicleRead := &tests.Vehicle{Meta: &tests.MotorMeta{}}
+	if err := DB.Debug().First(vehicleRead, "id = ?", vehicleWrite.ID).Error; err != nil {
+		t.Fatalf("fail to find vehicle %v", err)
+	} else {
+		AssertEqual(t, vehicleWrite.Meta.(*tests.MotorMeta).Power, vehicleRead.Meta.(*tests.MotorMeta).Power)
+	}
+}

tests/tests_test.go

@@ -11,6 +11,7 @@ import (
 	"gorm.io/driver/postgres"
 	"gorm.io/driver/sqlite"
 	"gorm.io/driver/sqlserver"
+
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
 	. "gorm.io/gorm/utils/tests"
@@ -107,7 +108,7 @@ func OpenTestConnection() (db *gorm.DB, err error) {
 
 func RunMigrations() {
 	var err error
-	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}, &Coupon{}, &CouponProduct{}, &Order{}, &Parent{}, &Child{}}
+	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}, &Coupon{}, &CouponProduct{}, &Order{}, &Parent{}, &Child{}, &Vehicle{Meta: &MotorMeta{}}}
 	rand.Seed(time.Now().UnixNano())
 	rand.Shuffle(len(allModels), func(i, j int) { allModels[i], allModels[j] = allModels[j], allModels[i] })
 

utils/tests/models.go

@@ -2,6 +2,10 @@ package tests
 
 import (
 	"database/sql"
+	"database/sql/driver"
+	"encoding/json"
+	"errors"
+	"fmt"
 	"time"
 
 	"gorm.io/gorm"
@@ -94,3 +98,62 @@ type Child struct {
 	ParentID *uint
 	Parent   *Parent
 }
+
+type Meta interface {
+	Scan(src interface{}) error
+	Value() (driver.Value, error)
+	GormDataType() string
+}
+type MotorMeta struct {
+	Power string
+}
+
+func (meta *MotorMeta) Scan(src interface{}) error {
+	bytes, ok := src.([]byte)
+	if !ok {
+		return errors.New(fmt.Sprint("Failed to unmarshal JSON value:", src))
+	}
+	result := MotorMeta{}
+	err := json.Unmarshal(bytes, &result)
+	*meta = result
+	return err
+}
+func (meta *MotorMeta) Value() (driver.Value, error) {
+	if meta == nil {
+		return nil, nil
+	}
+	res, err := json.Marshal(meta)
+	return string(res), err
+}
+func (MotorMeta) GormDataType() string {
+	return "json"
+}
+
+type ManualMeta struct {
+}
+
+func (meta *ManualMeta) Scan(src interface{}) error {
+	bytes, ok := src.([]byte)
+	if !ok {
+		return errors.New(fmt.Sprint("Failed to unmarshal JSON value:", src))
+	}
+	result := ManualMeta{}
+	err := json.Unmarshal(bytes, &result)
+	*meta = result
+	return err
+}
+func (meta *ManualMeta) Value() (driver.Value, error) {
+	if meta == nil {
+		return nil, nil
+	}
+	res, err := json.Marshal(meta)
+	return string(res), err
+}
+func (ManualMeta) GormDataType() string {
+	return "json"
+}
+
+type Vehicle struct {
+	gorm.Model
+	Meta Meta
+}