Add db.SettingsTypeFilter struct to db package

db/db.go

@@ -72,6 +72,7 @@ func Connect() *gorm.DB {
 	gormDB.AutoMigrate(&Metric{})
 	gormDB.AutoMigrate(&Currency{})
 	gormDB.AutoMigrate(&ExchangeRate{})
+	gormDB.AutoMigrate(&SettingsTypeFilter{})
 	return newUDB
 }
 

db/settings_type_filter.go

@@ -0,0 +1,36 @@
+package db
+
+import (
+	"errors"
+
+	"gorm.io/gorm"
+)
+
+type SettingsTypeFilter struct {
+	gorm.Model
+	UserID uint
+	User   *User
+	TypeID uint
+	Type   *Type
+}
+
+// so `SETTINGS_TYPE` is the NAME of struct that has such error
+// second `TYPE` means SettingsTypeFilter's Type fields are causing errors
+var (
+	ERROR_SETTINGS_TYPE_TYPEID_ZERO    = errors.New("SettingsTypeFilter's `TypeID` is zero")
+	ERROR_SETTINGS_TYPE_USERID_INVALID = errors.New("SettingsTypeFilter's `UserID` and Type's `UserID` are not equal")
+)
+
+func (st *SettingsTypeFilter) BeforeSave(tx *gorm.DB) error {
+	if st.TypeID == 0 {
+		return ERROR_SETTINGS_TYPE_TYPEID_ZERO
+	}
+	dbType := &Type{}
+	if err := tx.Find(dbType, st.TypeID).Error; err != nil {
+		return err
+	}
+	if dbType.UserID != st.UserID {
+		return ERROR_SETTINGS_TYPE_USERID_INVALID
+	}
+	return nil
+}