fix: Copy to an invalid addr but can set is not effective.

copier.go

@@ -102,7 +102,12 @@ func copier(toValue interface{}, fromValue interface{}, opt Option) (err error)
 	)
 
 	if !to.CanAddr() {
-		return ErrInvalidCopyDestination
+		toPtr := preIndirect(reflect.ValueOf(toValue))
+		if !toPtr.CanSet() {
+			return ErrInvalidCopyDestination
+		}
+		to = reflect.New(toPtr.Type().Elem())
+		toPtr.Set(to)
 	}
 
 	// Return is from value is invalid
@@ -433,6 +438,16 @@ func deepFields(reflectType reflect.Type) []reflect.StructField {
 	return res
 }
 
+func preIndirect(reflectValue reflect.Value) reflect.Value {
+	for reflectValue.Kind() == reflect.Ptr {
+		if !reflectValue.Elem().CanAddr() {
+			break
+		}
+		reflectValue = reflectValue.Elem()
+	}
+	return reflectValue
+}
+
 func indirect(reflectValue reflect.Value) reflect.Value {
 	for reflectValue.Kind() == reflect.Ptr {
 		reflectValue = reflectValue.Elem()

copier_test.go

@@ -1666,3 +1666,18 @@ func TestSqlNullFiled(t *testing.T) {
 		t.Errorf("to (%v) value should equal from (%v) value", to.MkExpiryDateType, from.MkExpiryDateType.Int32)
 	}
 }
+
+func TestCopy(t *testing.T) {
+	now := time.Now()
+	age := int32(28)
+	src := &User{
+		Age:      14,
+		Name:     "tom",
+		Birthday: &now,
+		FakeAge:  &age,
+		Notes:    []string{"hello"},
+	}
+	var tar *User
+	err := copier.Copy(&tar, src)
+	fmt.Println(err, tar, reflect.DeepEqual(src, tar))
+}