Add ORDER BY sql expression support

main.go

@@ -166,7 +166,10 @@ func (s *DB) Offset(offset interface{}) *DB {
 }
 
 // Order specify order when retrieve records from database, set reorder to `true` to overwrite defined conditions
-func (s *DB) Order(value string, reorder ...bool) *DB {
+//     db.Order("name DESC")
+//     db.Order("name DESC", true) // reorder
+//     db.Order(gorm.Expr("name = ? DESC", "first")) // sql expression
+func (s *DB) Order(value interface{}, reorder ...bool) *DB {
 	return s.clone().search.Order(value, reorder...).db
 }
 

query_test.go

@@ -307,6 +307,12 @@ func TestOrderAndPluck(t *testing.T) {
 	DB.Save(&user1).Save(&user2).Save(&user3)
 	scopedb := DB.Model(&User{}).Where("name like ?", "%OrderPluckUser%")
 
+	var user User
+	scopedb.Order(gorm.Expr("name = ? DESC", "OrderPluckUser2")).First(&user)
+	if user.Name != "OrderPluckUser2" {
+		t.Errorf("Order with sql expression")
+	}
+
 	var ages []int64
 	scopedb.Order("age desc").Pluck("age", &ages)
 	if ages[0] != 20 {

scope.go

@@ -730,7 +730,15 @@ func (scope *Scope) orderSQL() string {
 
 	var orders []string
 	for _, order := range scope.Search.orders {
-		orders = append(orders, scope.quoteIfPossible(order))
+		if str, ok := order.(string); ok {
+			orders = append(orders, scope.quoteIfPossible(str))
+		} else if expr, ok := order.(*expr); ok {
+			exp := expr.expr
+			for _, arg := range expr.args {
+				exp = strings.Replace(exp, "?", scope.AddToVars(arg), 1)
+			}
+			orders = append(orders, exp)
+		}
 	}
 	return " ORDER BY " + strings.Join(orders, ",")
 }

search.go

@@ -13,7 +13,7 @@ type search struct {
 	assignAttrs      []interface{}
 	selects          map[string]interface{}
 	omits            []string
-	orders           []string
+	orders           []interface{}
 	preload          []searchPreload
 	offset           interface{}
 	limit            interface{}
@@ -59,14 +59,12 @@ func (s *search) Assign(attrs ...interface{}) *search {
 	return s
 }
 
-func (s *search) Order(value string, reorder ...bool) *search {
+func (s *search) Order(value interface{}, reorder ...bool) *search {
 	if len(reorder) > 0 && reorder[0] {
-		if value != "" {
-			s.orders = []string{value}
-		} else {
-			s.orders = []string{}
-		}
-	} else if value != "" {
+		s.orders = []interface{}{}
+	}
+
+	if value != nil {
 		s.orders = append(s.orders, value)
 	}
 	return s