c++ - QML 对象属性的部分序列化

Question

我需要在 C++ 中序列化 QML 对象的一些属性

示例如下:

import QtQuick 2.0

Rectangle {
    property color fromcolor: "#0000FF"
    property color tocolor: "#000000"
    property int speed: 5000

    // brave workaround :)
    readonly property string serializable_properties: "fromcolor,tocolor,speed"
    ...
}

我只需要序列化 ​​serializable_properties 给定的属性。

有没有更好的方法来标记要序列化的属性而不用在字符串中列出它们的名称？这是为了防止更改属性名称时出现错误。

到目前为止，我使用 serializable_properties 如下:

const QMetaObject *metaobject = object->metaObject();
int count = metaobject->propertyCount();
for (int i=0; i<count; ++i)
{
    QMetaProperty metaproperty = metaobject->property(i);
    const char *name = metaproperty.name();
    QVariant value = object->property(name);

    qDebug() << name << value;
}

更新:

谢谢你的回答，我改进了这个方法如下:

• 枚举类的所有属性，但带有后缀的属性除外"_p"标记为私有(private)。

  const QObject *object = qobject_cast<QObject *>( qml_object );
  const QMetaObject *metaobject = object->metaObject();
  int count = metaobject->propertyCount();
  
  for (int i=metaobject->propertyOffset(); i<count; ++i)
  {
      QMetaProperty metaproperty = metaobject->property(i);
      const char *name = metaproperty.name();
      const QString p_name = QString::fromLatin1(name);
      QVariant value = object->property(name);
  
      if( p_name.endsWith(QStringLiteral("_p")) ) continue;
  
      qDebug() << name << value;
  }
  

和最终的 QML:

Rectangle {
    id: this
    property color fromcolor: "#0000FF"
    property color tocolor: "#000000"
    property int speed: 5000
    property alias mwidth: this.width  // if you want to serialize parent class width
    property int internal_var_p: 5
}

Answer 1

最简单的方法可能是为属性名称添加前缀或后缀。这样的前缀/后缀可以在遍历属性列表时轻松检测到。比如，您的属性可以以 ser 开头，或以 _ 结尾:

Rectangle {
    // prefix variant
    property color serFromColor: "#0000FF"
    property color serToColor: "#000000"
    // suffix variant
    property color fromcolor_: "#0000FF"
    property color tocolor_: "#000000"
}

对于后缀变体，序列化将如下所示:

QDataStream stream;
const QMetaObject *metaObject = object->metaObject();
int count = metaObject->propertyCount();
// You can start iterating from metaObject->propertyOffset() if you
// are not interested in properties of parent objects.
for (int i=0; i<count; ++i)
{
    QMetaProperty property = metaObject->property(i);
    const char *name = property.name();
    const QString sName = QString::fromLatin1(name);
    if (! sName.endsWith(QStringLiteral("_"))) continue;
    QVariant value = object->property(name);
    stream << sName << value;    
    qDebug() << name << value;
}

对于前缀变体，您需要检查 3 个条件:

1. 姓名超过 3 个字符。
2. 姓名以“ser”开头。
3. 如果name[3]是字母，则必须是大写字母。