Исходники и презентации

lessons/generics_and_reflection/private_fields_1/main.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"unsafe"
+)
+
+type Data struct {
+	age     int8
+	address string
+}
+
+func getFieldOffset(instance interface{}, fieldName string) (uintptr, error) {
+	instanceValue := reflect.ValueOf(instance)
+	if instanceValue.Kind() != reflect.Ptr {
+		return 0, fmt.Errorf("the first parameter must be a pointer to a struct")
+	}
+
+	instanceType := instanceValue.Type().Elem()
+	field, found := instanceType.FieldByName(fieldName)
+	if !found {
+		return 0, fmt.Errorf("field '%s' not found in the struct", fieldName)
+	}
+
+	return field.Offset, nil
+}
+
+func AssignPrivateField[T any, V any](src *T, field string, value V) error {
+	offset, err := getFieldOffset(src, field)
+	if err != nil {
+		return fmt.Errorf("get offset: %w", err)
+	}
+
+	fieldPtr := (*V)(unsafe.Add(unsafe.Pointer(src), offset))
+	*fieldPtr = value
+	return nil
+}
+
+func ReadPrivateField[T any, V any](src *T, field string) (V, error) {
+	var output V
+
+	offset, err := getFieldOffset(src, field)
+	if err != nil {
+		return output, fmt.Errorf("get offset: %w", err)
+	}
+
+	output = *(*V)(unsafe.Add(unsafe.Pointer(src), offset))
+	return output, nil
+}
+
+func main() {
+	data := &Data{}
+	_ = AssignPrivateField(data, "address", "Moscow")
+	fmt.Println(data)
+}