add new functions and create folder of db path if nonexisting

dbHandler.go

@@ -3,6 +3,7 @@ package dbHandler
 import (
 	"errors"
 	"fmt"
+	"os"
 	"path/filepath"
 	"reflect"
 	"strings"
@@ -57,12 +58,30 @@ func NewDBHandler(name, path string, logger *logging.Logger) (dH *DBHandler, err
 	if filepath.Ext(name) == "" {
 		name += ".db"
 	}
+
+	if path != "" {
+		if _, err := os.Stat(path); err != nil {
+			if err := os.MkdirAll(path, 0666); err != err {
+				return nil, err
+			}
+		}
+	}
+
 	dbPath := filepath.Join(path, name)
 	logger.Debug("NewDBHandler", "open database "+dbPath)
 	dH.db, err = gorm.Open(sqlite.Open(dbPath), &gorm.Config{})
 	return
 }
 
+// close DB
+func (dH *DBHandler) Close() error {
+	sqlDB, err := dH.db.DB()
+	if err != nil {
+		return err
+	}
+	return sqlDB.Close()
+}
+
 // addNewTable
 //
 // Description:
@@ -302,3 +321,24 @@ func (dH *DBHandler) Exists(model any, key string, value any, likeSearch bool) (
 	}
 	return tx.RowsAffected > 0
 }
+
+func (dH *DBHandler) GetByIdWithRelation(model any, relation string, id uint) error {
+	if id == 0 {
+		return dH.db.Preload(relation).Find(model).Error
+	}
+
+	// Load member AND its events
+	err := dH.db.Preload(relation).First(model, id).Error
+
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return fmt.Errorf("no record found for id: %v", id)
+	} else if err != nil {
+		return fmt.Errorf("query failed: %w", err)
+	}
+	return nil
+}
+
+func (dH *DBHandler) AddRelation(model, relation any, relationName string) error {
+	return dH.db.Model(model).Association(relationName).Append(relation)
+
+}

db_test.go

@@ -0,0 +1,82 @@
+package dbHandler
+
+import (
+	"os"
+	"testing"
+)
+
+type Event struct {
+	Id        int       `gorm:"primaryKey" json:"id"`
+	Name      string    `gorm:"column:name" json:"name"`
+	Attendees []*Member `gorm:"many2many:member_events;"`
+}
+
+type Member struct {
+	Id        int      `gorm:"primaryKey" json:"id"`
+	FirstName string   `gorm:"column:firstName" json:"firstName,omitempty"`
+	LastName  string   `gorm:"column:lastName" json:"lastName,omitempty"`
+	Events    []*Event `gorm:"many2many:member_events;" json:"events"`
+}
+
+func TestDbHandler(t *testing.T) {
+
+	dbHandler, err := NewDBHandler("test.db", "test", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := dbHandler.AddNewTable(&Member{}); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := dbHandler.AddNewTable(&Event{}); err != nil {
+		t.Fatal(err)
+	}
+
+	member := &Member{FirstName: "adrian", LastName: "zuercher"}
+	dbHandler.AddNewColum(member)
+	event := &Event{
+		Name: "testEvent",
+	}
+	dbHandler.AddNewColum(event)
+	dbHandler.AddRelation(event, member, "Attendees")
+
+	var members []Member
+	if err := dbHandler.GetById(&members, 0); err != nil {
+		t.Fatal(err)
+	}
+	t.Log(members)
+
+	if err := dbHandler.GetByIdWithRelation(&members, "Events", 0); err != nil {
+		t.Fatal(err)
+	}
+	t.Log(members)
+
+	for _, member := range members {
+		t.Log("Member:", member.FirstName, member.LastName)
+		for _, event := range member.Events {
+			t.Log("Event:", event)
+		}
+	}
+
+	var events []Event
+
+	if err := dbHandler.GetByIdWithRelation(&events, "Attendees", 0); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, event := range events {
+		t.Log("event:", event.Name)
+		for _, member := range event.Attendees {
+			t.Log("attendee:", member)
+		}
+	}
+
+	if err := dbHandler.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := os.RemoveAll("test"); err != nil {
+		t.Fatal(err)
+	}
+}