added error types for easier error handling with cases

callback_query.go

@@ -79,7 +79,7 @@ func queryCallback(scope *Scope) {
 			}
 
 			if scope.db.RowsAffected == 0 && !isSlice {
-				scope.Err(ErrRecordNotFound)
+				scope.Err(NewErrRecordNotFound())
 			}
 		}
 	}

errors.go

@@ -5,19 +5,6 @@ import (
 	"strings"
 )
 
-var (
-	// ErrRecordNotFound record not found error, happens when haven't find any matched data when looking up with a struct
-	ErrRecordNotFound = errors.New("record not found")
-	// ErrInvalidSQL invalid SQL error, happens when you passed invalid SQL
-	ErrInvalidSQL = errors.New("invalid SQL")
-	// ErrInvalidTransaction invalid transaction when you are trying to `Commit` or `Rollback`
-	ErrInvalidTransaction = errors.New("no valid transaction")
-	// ErrCantStartTransaction can't start transaction when you are trying to start one with `Begin`
-	ErrCantStartTransaction = errors.New("can't start transaction")
-	// ErrUnaddressable unaddressable value
-	ErrUnaddressable = errors.New("using unaddressable value")
-)
-
 type errorsInterface interface {
 	GetErrors() []error
 }
@@ -32,6 +19,36 @@ func (errs Errors) GetErrors() []error {
 	return errs.errors
 }
 
+type ErrRecordNotFound struct{ error }
+
+type ErrInvalidSQL struct{ error }
+
+type ErrInvalidTransaction struct{ error }
+
+type ErrCantStartTransaction struct{ error }
+
+type ErrUnaddressable struct{ error }
+
+func NewErrRecordNotFound() error {
+	return ErrRecordNotFound{errors.New("record not found")}
+}
+
+func NewErrInvalidSQL() error {
+	return ErrInvalidSQL{errors.New("invalid SQL")}
+}
+
+func NewErrInvalidTransaction() error {
+	return ErrCantStartTransaction{errors.New("no valid transaction")}
+}
+
+func NewErrCantStartTransaction() error {
+	return ErrCantStartTransaction{errors.New("can't start transaction")}
+}
+
+func NewErrUnaddressable() error {
+	return ErrUnaddressable{errors.New("using unaddressable value")}
+}
+
 // Add add an error
 func (errs *Errors) Add(err error) {
 	if errors, ok := err.(errorsInterface); ok {

field.go

@@ -21,7 +21,7 @@ func (field *Field) Set(value interface{}) (err error) {
 	}
 
 	if !field.Field.CanAddr() {
-		return ErrUnaddressable
+		return NewErrUnaddressable()
 	}
 
 	reflectValue, ok := value.(reflect.Value)

main.go

@@ -424,7 +424,7 @@ func (s *DB) Begin() *DB {
 		c.db = interface{}(tx).(sqlCommon)
 		c.AddError(err)
 	} else {
-		c.AddError(ErrCantStartTransaction)
+		c.AddError(NewErrCantStartTransaction())
 	}
 	return c
 }
@@ -434,7 +434,7 @@ func (s *DB) Commit() *DB {
 	if db, ok := s.db.(sqlTx); ok {
 		s.AddError(db.Commit())
 	} else {
-		s.AddError(ErrInvalidTransaction)
+		s.AddError(NewErrInvalidTransaction())
 	}
 	return s
 }
@@ -444,7 +444,7 @@ func (s *DB) Rollback() *DB {
 	if db, ok := s.db.(sqlTx); ok {
 		s.AddError(db.Rollback())
 	} else {
-		s.AddError(ErrInvalidTransaction)
+		s.AddError(NewErrInvalidTransaction())
 	}
 	return s
 }
@@ -457,7 +457,7 @@ func (s *DB) NewRecord(value interface{}) bool {
 // RecordNotFound check if returning ErrRecordNotFound error
 func (s *DB) RecordNotFound() bool {
 	for _, err := range s.GetErrors() {
-		if err == ErrRecordNotFound {
+		if _, ok := err.(ErrRecordNotFound); ok {
 			return true
 		}
 	}
@@ -633,7 +633,7 @@ func (s *DB) SetJoinTableHandler(source interface{}, column string, handler Join
 // AddError add error to the db
 func (s *DB) AddError(err error) error {
 	if err != nil {
-		if err != ErrRecordNotFound {
+		if _, ok := err.(ErrRecordNotFound); !ok {
 			if s.logMode == 0 {
 				go s.print(fileWithLineNum(), err)
 			} else {

main_test.go

@@ -479,7 +479,7 @@ func TestRaw(t *testing.T) {
 	}
 
 	DB.Exec("update users set name=? where name in (?)", "jinzhu", []string{user1.Name, user2.Name, user3.Name})
-	if DB.Where("name in (?)", []string{user1.Name, user2.Name, user3.Name}).First(&User{}).Error != gorm.ErrRecordNotFound {
+	if _, ok := DB.Where("name in (?)", []string{user1.Name, user2.Name, user3.Name}).First(&User{}).Error.(gorm.ErrRecordNotFound); !ok {
 		t.Error("Raw sql to update records")
 	}
 }
@@ -709,7 +709,7 @@ func TestOpenExistingDB(t *testing.T) {
 	}
 
 	var user User
-	if db.Where("name = ?", "jnfeinstein").First(&user).Error == gorm.ErrRecordNotFound {
+	if _, ok := db.Where("name = ?", "jnfeinstein").First(&user).Error.(gorm.ErrRecordNotFound); ok {
 		t.Errorf("Should have found existing record")
 	}
 }

preload_test.go

@@ -133,7 +133,7 @@ func TestNestedPreload1(t *testing.T) {
 		t.Errorf("got %s; want %s", toJSONString(got), toJSONString(want))
 	}
 
-	if err := DB.Preload("Level2").Preload("Level2.Level1").Find(&got, "name = ?", "not_found").Error; err != gorm.ErrRecordNotFound {
+	if err, ok := DB.Preload("Level2").Preload("Level2.Level1").Find(&got, "name = ?", "not_found").Error.(gorm.ErrRecordNotFound); !ok {
 		t.Error(err)
 	}
 }
@@ -981,7 +981,7 @@ func TestNestedManyToManyPreload(t *testing.T) {
 		t.Errorf("got %s; want %s", toJSONString(got), toJSONString(want))
 	}
 
-	if err := DB.Preload("Level2s.Level1s").Find(&got, "value = ?", "not_found").Error; err != gorm.ErrRecordNotFound {
+	if err, ok := DB.Preload("Level2s.Level1s").Find(&got, "value = ?", "not_found").Error.(gorm.ErrRecordNotFound); !ok {
 		t.Error(err)
 	}
 }
@@ -1038,7 +1038,7 @@ func TestNestedManyToManyPreload2(t *testing.T) {
 		t.Errorf("got %s; want %s", toJSONString(got), toJSONString(want))
 	}
 
-	if err := DB.Preload("Level2.Level1s").Find(&got, "value = ?", "not_found").Error; err != gorm.ErrRecordNotFound {
+	if err, ok := DB.Preload("Level2.Level1s").Find(&got, "value = ?", "not_found").Error.(gorm.ErrRecordNotFound); !ok {
 		t.Error(err)
 	}
 }

scope.go

@@ -850,7 +850,7 @@ func (scope *Scope) updatedAttrsWithValues(value interface{}) (results map[strin
 				err := field.Set(value)
 				if field.IsNormal {
 					hasUpdate = true
-					if err == ErrUnaddressable {
+					if _, ok := err.(ErrUnaddressable); ok {
 						fmt.Println(err)
 						results[field.DBName] = value
 					} else {

search.go

@@ -139,7 +139,7 @@ func (s *search) getInterfaceAsSQL(value interface{}) (str string) {
 	case string, int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
 		str = fmt.Sprintf("%v", value)
 	default:
-		s.db.AddError(ErrInvalidSQL)
+		s.db.AddError(NewErrInvalidSQL())
 	}
 
 	if str == "-1" {