diff --git a/callback_create.go b/callback_create.go
index 6054aa91..11082f8a 100644
--- a/callback_create.go
+++ b/callback_create.go
@@ -5,6 +5,20 @@ import (
 	"strings"
 )
 
+// Define callbacks for creating
+func init() {
+	defaultCallback.Create().Register("gorm:begin_transaction", beginTransactionCallback)
+	defaultCallback.Create().Register("gorm:before_create", beforeCreateCallback)
+	defaultCallback.Create().Register("gorm:save_before_associations", saveBeforeAssociationsCallback)
+	defaultCallback.Create().Register("gorm:update_time_stamp_when_create", updateTimeStampForCreateCallback)
+	defaultCallback.Create().Register("gorm:create", createCallback)
+	defaultCallback.Create().Register("gorm:force_reload_after_create", forceReloadAfterCreateCallback)
+	defaultCallback.Create().Register("gorm:save_after_associations", saveAfterAssociationsCallback)
+	defaultCallback.Create().Register("gorm:after_create", afterCreateCallback)
+	defaultCallback.Create().Register("gorm:commit_or_rollback_transaction", commitOrRollbackTransactionCallback)
+}
+
+// beforeCreateCallback will invoke `BeforeSave`, `BeforeCreate` method before creating
 func beforeCreateCallback(scope *Scope) {
 	if !scope.HasError() {
 		scope.CallMethod("BeforeSave")
@@ -14,6 +28,7 @@ func beforeCreateCallback(scope *Scope) {
 	}
 }
 
+// updateTimeStampForCreateCallback will set `CreatedAt`, `UpdatedAt` when creating
 func updateTimeStampForCreateCallback(scope *Scope) {
 	if !scope.HasError() {
 		now := NowFunc()
@@ -22,6 +37,7 @@ func updateTimeStampForCreateCallback(scope *Scope) {
 	}
 }
 
+// createCallback the callback used to insert data into database
 func createCallback(scope *Scope) {
 	defer scope.trace(NowFunc())
 
@@ -106,12 +122,14 @@ func createCallback(scope *Scope) {
 	}
 }
 
+// forceReloadAfterCreateCallback will reload columns that having default value, and set it back to current object
 func forceReloadAfterCreateCallback(scope *Scope) {
 	if columns, ok := scope.InstanceGet("gorm:force_reload_after_create_attrs"); ok {
 		scope.DB().New().Select(columns.([]string)).First(scope.Value)
 	}
 }
 
+// beforeCreateCallback will invoke `AfterCreate`, `AfterSave` method after creating
 func afterCreateCallback(scope *Scope) {
 	if !scope.HasError() {
 		scope.CallMethod("AfterCreate")
@@ -120,15 +138,3 @@ func afterCreateCallback(scope *Scope) {
 		scope.CallMethod("AfterSave")
 	}
 }
-
-func init() {
-	defaultCallback.Create().Register("gorm:begin_transaction", beginTransactionCallback)
-	defaultCallback.Create().Register("gorm:before_create", beforeCreateCallback)
-	defaultCallback.Create().Register("gorm:save_before_associations", saveBeforeAssociationsCallback)
-	defaultCallback.Create().Register("gorm:update_time_stamp_when_create", updateTimeStampForCreateCallback)
-	defaultCallback.Create().Register("gorm:create", createCallback)
-	defaultCallback.Create().Register("gorm:force_reload_after_create", forceReloadAfterCreateCallback)
-	defaultCallback.Create().Register("gorm:save_after_associations", saveAfterAssociationsCallback)
-	defaultCallback.Create().Register("gorm:after_create", afterCreateCallback)
-	defaultCallback.Create().Register("gorm:commit_or_rollback_transaction", commitOrRollbackTransactionCallback)
-}
diff --git a/callback_delete.go b/callback_delete.go
index 804bdf71..17b5cfb4 100644
--- a/callback_delete.go
+++ b/callback_delete.go
@@ -2,6 +2,14 @@ package gorm
 
 import "fmt"
 
+func init() {
+	defaultCallback.Delete().Register("gorm:begin_transaction", beginTransactionCallback)
+	defaultCallback.Delete().Register("gorm:before_delete", beforeDeleteCallback)
+	defaultCallback.Delete().Register("gorm:delete", deleteCallback)
+	defaultCallback.Delete().Register("gorm:after_delete", afterDeleteCallback)
+	defaultCallback.Delete().Register("gorm:commit_or_rollback_transaction", commitOrRollbackTransactionCallback)
+}
+
 func beforeDeleteCallback(scope *Scope) {
 	if !scope.HasError() {
 		scope.CallMethod("BeforeDelete")
@@ -30,11 +38,3 @@ func afterDeleteCallback(scope *Scope) {
 		scope.CallMethod("AfterDelete")
 	}
 }
-
-func init() {
-	defaultCallback.Delete().Register("gorm:begin_transaction", beginTransactionCallback)
-	defaultCallback.Delete().Register("gorm:before_delete", beforeDeleteCallback)
-	defaultCallback.Delete().Register("gorm:delete", deleteCallback)
-	defaultCallback.Delete().Register("gorm:after_delete", afterDeleteCallback)
-	defaultCallback.Delete().Register("gorm:commit_or_rollback_transaction", commitOrRollbackTransactionCallback)
-}
diff --git a/callback_query.go b/callback_query.go
index 9ebff6b7..f6fa0aa1 100644
--- a/callback_query.go
+++ b/callback_query.go
@@ -6,6 +6,12 @@ import (
 	"reflect"
 )
 
+func init() {
+	defaultCallback.Query().Register("gorm:query", queryCallback)
+	defaultCallback.Query().Register("gorm:after_query", afterQueryCallback)
+	defaultCallback.Query().Register("gorm:preload", preloadCallback)
+}
+
 func queryCallback(scope *Scope) {
 	defer scope.trace(NowFunc())
 
@@ -83,9 +89,3 @@ func afterQueryCallback(scope *Scope) {
 		scope.CallMethod("AfterFind")
 	}
 }
-
-func init() {
-	defaultCallback.Query().Register("gorm:query", queryCallback)
-	defaultCallback.Query().Register("gorm:after_query", afterQueryCallback)
-	defaultCallback.Query().Register("gorm:preload", preloadCallback)
-}
diff --git a/callback_shared.go b/callback_save.go
similarity index 100%
rename from callback_shared.go
rename to callback_save.go
diff --git a/callback_update.go b/callback_update.go
index 9463c994..b9d2bcbc 100644
--- a/callback_update.go
+++ b/callback_update.go
@@ -5,6 +5,18 @@ import (
 	"strings"
 )
 
+func init() {
+	defaultCallback.Update().Register("gorm:assign_update_attributes", assignUpdateAttributesCallback)
+	defaultCallback.Update().Register("gorm:begin_transaction", beginTransactionCallback)
+	defaultCallback.Update().Register("gorm:before_update", beforeUpdateCallback)
+	defaultCallback.Update().Register("gorm:save_before_associations", saveBeforeAssociationsCallback)
+	defaultCallback.Update().Register("gorm:update_time_stamp_when_update", updateTimeStampForUpdateCallback)
+	defaultCallback.Update().Register("gorm:update", updateCallback)
+	defaultCallback.Update().Register("gorm:save_after_associations", saveAfterAssociationsCallback)
+	defaultCallback.Update().Register("gorm:after_update", afterUpdateCallback)
+	defaultCallback.Update().Register("gorm:commit_or_rollback_transaction", commitOrRollbackTransactionCallback)
+}
+
 func assignUpdateAttributesCallback(scope *Scope) {
 	if attrs, ok := scope.InstanceGet("gorm:update_interface"); ok {
 		if maps := convertInterfaceToMap(attrs); len(maps) > 0 {
@@ -89,15 +101,3 @@ func afterUpdateCallback(scope *Scope) {
 		}
 	}
 }
-
-func init() {
-	defaultCallback.Update().Register("gorm:assign_update_attributes", assignUpdateAttributesCallback)
-	defaultCallback.Update().Register("gorm:begin_transaction", beginTransactionCallback)
-	defaultCallback.Update().Register("gorm:before_update", beforeUpdateCallback)
-	defaultCallback.Update().Register("gorm:save_before_associations", saveBeforeAssociationsCallback)
-	defaultCallback.Update().Register("gorm:update_time_stamp_when_update", updateTimeStampForUpdateCallback)
-	defaultCallback.Update().Register("gorm:update", updateCallback)
-	defaultCallback.Update().Register("gorm:save_after_associations", saveAfterAssociationsCallback)
-	defaultCallback.Update().Register("gorm:after_update", afterUpdateCallback)
-	defaultCallback.Update().Register("gorm:commit_or_rollback_transaction", commitOrRollbackTransactionCallback)
-}