fix: update associations

internal/database/database.go

@@ -2,13 +2,14 @@ package database
 
 import (
 	"app/internal/dal"
-	"gorm.io/driver/sqlite"
-	"gorm.io/gorm"
-	"gorm.io/gorm/logger"
 	"log"
 	"os"
 	"sync"
 	"time"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
 )
 
 var (
@@ -31,7 +32,8 @@ func initialize() error {
 		},
 	)
 	db, err = gorm.Open(sqlite.Open("file:"+Path+"?_fk=1"), &gorm.Config{
-		Logger: newLogger,
+		Logger:               newLogger,
+		FullSaveAssociations: false,
 	})
 	if err != nil {
 		return err

internal/gen/gen.go

@@ -1,17 +1,18 @@
 package main
 
 import (
-  "gorm.io/gen"
-  "app/internal/models"
+	"app/internal/models"
+
+	"gorm.io/gen"
 )
 
 func main() {
-  g := gen.NewGenerator(gen.Config{
-     OutPath: "../dal", // output directory, default value is ./query
-     Mode:    gen.WithDefaultQuery | gen.WithQueryInterface | gen.WithoutContext,
-     FieldNullable: true,
-     WithUnitTest: true,
-  })
-  g.ApplyBasic(models.Entities...)
-  g.Execute()
+	g := gen.NewGenerator(gen.Config{
+		OutPath:       "../dal", // output directory, default value is ./query
+		Mode:          gen.WithDefaultQuery | gen.WithQueryInterface | gen.WithoutContext,
+		FieldNullable: true,
+		WithUnitTest:  true,
+	})
+	g.ApplyBasic(models.Entities...)
+	g.Execute()
 }

internal/services/author.go

@@ -2,6 +2,7 @@ package services
 
 import (
 	"app/internal/dal"
+	"app/internal/database"
 	"app/internal/models"
 	"errors"
 
@@ -13,6 +14,7 @@ type AuthorService struct{}
 type Author = models.Author
 
 func (service *AuthorService) Create(item Author) (Author, error) {
+	ReplaceEmptySlicesWithNil(&item)
 	err := dal.Author.Preload(field.Associations).Create(&item)
 	return item, err
 }
@@ -32,15 +34,24 @@ func (service *AuthorService) GetById(id uint) (*Author, error) {
 	}
 	return item, nil
 }
+
 func (service *AuthorService) Update(item Author) (Author, error) {
-	var posts []*models.Post
-	for _, post := range item.Posts {
-		posts = append(posts, &post)
+	ReplaceEmptySlicesWithNil(&item)
+
+	_, err := dal.Author.Updates(&item)
+	if err != nil {
+		return item, err
 	}
-	err := dal.Author.Posts.Model(&item).Replace(posts...)
-	_ = dal.Author.Save(&item)
+
+	err = UpdateAssociations(database.GetInstance(), &item)
+
+	if err != nil {
+		return item, err
+	}
+
 	return item, err
 }
+
 func (service *AuthorService) Delete(id uint) error {
 	_, err := dal.Author.Unscoped().Where(dal.Author.Id.Eq(id)).Delete()
 	return err

internal/services/handle_nil.go

@@ -0,0 +1,49 @@
+package services
+
+import "reflect"
+
+// ReplaceEmptySlicesWithNil takes a pointer to any struct (or struct-like type)
+// and replaces all empty slices with nil, traversing nested fields recursively.
+func ReplaceEmptySlicesWithNil(v interface{}) {
+	// Must be a pointer so we can set fields
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr {
+		panic("ReplaceEmptySlicesWithNil expects a pointer to a struct")
+	}
+
+	replaceEmptySlices(rv.Elem())
+}
+
+// replaceEmptySlices is the recursive helper that does the actual reflection work.
+func replaceEmptySlices(v reflect.Value) {
+	switch v.Kind() {
+	case reflect.Ptr:
+		// If it is a pointer, recurse on the element it points to.
+		if !v.IsNil() {
+			replaceEmptySlices(v.Elem())
+		}
+
+	case reflect.Struct:
+		// For a struct, iterate each field and process it.
+		for i := 0; i < v.NumField(); i++ {
+			fieldVal := v.Field(i)
+			if !fieldVal.CanSet() {
+				// If we can't set the field (e.g. unexported), skip it
+				continue
+			}
+			replaceEmptySlices(fieldVal)
+		}
+
+	case reflect.Slice:
+		// If it is a slice, check if it's empty; if it is, set it to nil.
+		if v.Len() == 0 && v.CanSet() {
+			// v.Set(reflect.Zero(v.Type())) sets slice to nil
+			v.Set(reflect.Zero(v.Type()))
+		} else {
+			// If not empty, we should recurse on each element in case it's a struct.
+			for i := 0; i < v.Len(); i++ {
+				replaceEmptySlices(v.Index(i))
+			}
+		}
+	}
+}

internal/services/update_associations.go

@@ -0,0 +1,41 @@
+package services
+
+import (
+	"errors"
+	"reflect"
+
+	"gorm.io/gorm"
+)
+
+func UpdateAssociations(db *gorm.DB, item interface{}) error {
+    // We expect a pointer to a struct so we can do db.Model(item).
+    val := reflect.ValueOf(item)
+    if val.Kind() != reflect.Ptr {
+        return errors.New("item must be a pointer to a struct")
+    }
+
+    elem := val.Elem()
+    if elem.Kind() != reflect.Struct {
+        return errors.New("item must be a pointer to a struct")
+    }
+
+    t := elem.Type()
+    for i := 0; i < elem.NumField(); i++ {
+        fieldVal := elem.Field(i)
+        fieldType := t.Field(i)
+
+        // Only process exported fields (capitalized) and slices.
+        if fieldType.PkgPath == "" && fieldVal.Kind() == reflect.Slice {
+            // For clarity, the association name is the struct field name by default.
+            assocName := fieldType.Name
+
+            // Replace the association with the current slice value.
+            // If you only want to replace on non-nil or non-empty slices, you can add extra checks here.
+            if err := db.Model(item).Association(assocName).Replace(fieldVal.Interface()); err != nil {
+                return err
+            }
+        }
+    }
+
+    return nil
+}