From e60a8d54ff609e9ba74c2335b22a7c36decaa5fb Mon Sep 17 00:00:00 2001
From: Jinzhu <wosmvp@gmail.com>
Date: Sun, 24 May 2020 00:52:25 +0800
Subject: [PATCH] Test Nested Preload

---
 callbacks/preload.go  |  6 ++---
 schema/schema.go      |  2 +-
 schema/utils.go       | 12 ++++++---
 tests/preload_test.go | 58 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 8 deletions(-)
 create mode 100644 tests/preload_test.go

diff --git a/callbacks/preload.go b/callbacks/preload.go
index 7e3810b5..f48777c2 100644
--- a/callbacks/preload.go
+++ b/callbacks/preload.go
@@ -22,7 +22,7 @@ func preload(db *gorm.DB, rels []*schema.Relationship, conds []interface{}) {
 	)
 
 	if len(rels) > 1 {
-		reflectValue = schema.GetRelationsValues(reflectValue, rels[:len(rels)])
+		reflectValue = schema.GetRelationsValues(reflectValue, rels[:len(rels)-1])
 	}
 
 	if rel.JoinTable != nil {
@@ -107,9 +107,9 @@ func preload(db *gorm.DB, rels []*schema.Relationship, conds []interface{}) {
 				rel.Field.Set(data, reflectResults.Index(i).Interface())
 			case reflect.Slice, reflect.Array:
 				if reflectFieldValue.Type().Elem().Kind() == reflect.Ptr {
-					rel.Field.Set(data, reflect.Append(reflectFieldValue, reflectResults.Index(i).Addr()).Interface())
-				} else {
 					rel.Field.Set(data, reflect.Append(reflectFieldValue, reflectResults.Index(i)).Interface())
+				} else {
+					rel.Field.Set(data, reflect.Append(reflectFieldValue, reflectResults.Index(i).Elem()).Interface())
 				}
 			}
 		}
diff --git a/schema/schema.go b/schema/schema.go
index 79faae12..caae55ac 100644
--- a/schema/schema.go
+++ b/schema/schema.go
@@ -49,7 +49,7 @@ func (schema Schema) String() string {
 }
 
 func (schema Schema) MakeSlice() reflect.Value {
-	slice := reflect.MakeSlice(reflect.SliceOf(schema.ModelType), 0, 0)
+	slice := reflect.MakeSlice(reflect.SliceOf(reflect.PtrTo(schema.ModelType)), 0, 0)
 	results := reflect.New(slice.Type())
 	results.Elem().Set(slice)
 	return results
diff --git a/schema/utils.go b/schema/utils.go
index c47f1984..f7808f0e 100644
--- a/schema/utils.go
+++ b/schema/utils.go
@@ -55,17 +55,21 @@ func removeSettingFromTag(tag reflect.StructTag, name string) reflect.StructTag
 // GetRelationsValues get relations's values from a reflect value
 func GetRelationsValues(reflectValue reflect.Value, rels []*Relationship) (reflectResults reflect.Value) {
 	for _, rel := range rels {
-		reflectResults = reflect.MakeSlice(reflect.SliceOf(rel.FieldSchema.ModelType), 0, 0)
+		reflectResults = reflect.MakeSlice(reflect.SliceOf(reflect.PtrTo(rel.FieldSchema.ModelType)), 0, 0)
 
 		appendToResults := func(value reflect.Value) {
 			if _, isZero := rel.Field.ValueOf(value); !isZero {
 				result := reflect.Indirect(rel.Field.ReflectValueOf(value))
 				switch result.Kind() {
 				case reflect.Struct:
-					reflectResults = reflect.Append(reflectResults, result)
+					reflectResults = reflect.Append(reflectResults, result.Addr())
 				case reflect.Slice, reflect.Array:
-					for i := 0; i < value.Len(); i++ {
-						reflectResults = reflect.Append(reflectResults, reflect.Indirect(value.Index(i)))
+					for i := 0; i < result.Len(); i++ {
+						if result.Index(i).Kind() == reflect.Ptr {
+							reflectResults = reflect.Append(reflectResults, result.Index(i))
+						} else {
+							reflectResults = reflect.Append(reflectResults, result.Index(i).Addr())
+						}
 					}
 				}
 			}
diff --git a/tests/preload_test.go b/tests/preload_test.go
new file mode 100644
index 00000000..74f21f55
--- /dev/null
+++ b/tests/preload_test.go
@@ -0,0 +1,58 @@
+package tests_test
+
+import (
+	"strconv"
+	"testing"
+
+	. "github.com/jinzhu/gorm/tests"
+)
+
+func TestNestedPreload(t *testing.T) {
+	var user = *GetUser("nested_preload", Config{Pets: 2})
+
+	for idx, pet := range user.Pets {
+		pet.Toy = Toy{Name: "toy_nested_preload_" + strconv.Itoa(idx+1)}
+	}
+
+	if err := DB.Create(&user).Error; err != nil {
+		t.Fatalf("errors happened when create: %v", err)
+	}
+
+	var user2 User
+	DB.Preload("Pets.Toy").Find(&user2, "id = ?", user.ID)
+
+	CheckUser(t, user2, user)
+}
+
+func TestNestedPreloadForSlice(t *testing.T) {
+	var users = []User{
+		*GetUser("slice_nested_preload_1", Config{Pets: 2}),
+		*GetUser("slice_nested_preload_2", Config{Pets: 0}),
+		*GetUser("slice_nested_preload_3", Config{Pets: 3}),
+	}
+
+	for _, user := range users {
+		for idx, pet := range user.Pets {
+			pet.Toy = Toy{Name: user.Name + "_toy_nested_preload_" + strconv.Itoa(idx+1)}
+		}
+	}
+
+	if err := DB.Create(&users).Error; err != nil {
+		t.Fatalf("errors happened when create: %v", err)
+	}
+
+	var userIDs []uint
+	for _, user := range users {
+		userIDs = append(userIDs, user.ID)
+	}
+
+	var users2 []User
+	DB.Preload("Pets.Toy").Find(&users2, "id IN ?", userIDs)
+
+	for idx, user := range users2 {
+		CheckUser(t, user, users[idx])
+	}
+}
+
+func TestPreloadWithConds(t *testing.T) {
+}