QObject的setUserData和setProperty——Qt_xiaopei_yan的博客-CSDN博客前言很多时候需要界面存储一些数据或信息，这样可以根据这些数据或信息来了解或获取点什么。可以说给界面增加一个标记，让我们更容易辨识。我之前一直习惯给列表项QListWidgetItem或者树项QTreeWidgetItem携带一些数据，比如id，用setData来实现。所以这次就想QWidget有没有类似的方法，结果就找到了setUserData。后来在mac os中重新编译时，发现setUserData不可用了，建议用setProperty替换。用法我现在用的Qt的版本是Qt5.14 .https://blog.csdn.net/xiaopei_yan/article/details/106687148
 

QObjectUserData* userData(uint id) const;
void QObject::setUserData(uint id, QObjectUserData* data)
{
    Q_D(QObject);
    if (!d->extraData)
        d->extraData = new QObjectPrivate::ExtraData;

    if (d->extraData->userData.size() <= (int) id)
        d->extraData->userData.resize((int) id + 1);
    d->extraData->userData[id] = data;
}


QVariant property(const char *name) const;
bool QObject::setProperty(const char *name, const QVariant &value)
{
    Q_D(QObject);
    const QMetaObject* meta = metaObject();
    if (!name || !meta)
        return false;

    int id = meta->indexOfProperty(name);
    if (id < 0) {
        if (!d->extraData)
            d->extraData = new QObjectPrivate::ExtraData;

        const int idx = d->extraData->propertyNames.indexOf(name);

        if (!value.isValid()) {
            if (idx == -1)
                return false;
            d->extraData->propertyNames.removeAt(idx);
            d->extraData->propertyValues.removeAt(idx);
        } else {
            if (idx == -1) {
                d->extraData->propertyNames.append(name);
                d->extraData->propertyValues.append(value);
            } else {
                if (value.userType() == d->extraData->propertyValues.at(idx).userType()
                        && value == d->extraData->propertyValues.at(idx))
                    return false;
                d->extraData->propertyValues[idx] = value;
            }
        }

        QDynamicPropertyChangeEvent ev(name);
        QCoreApplication::sendEvent(this, &ev);

        return false;
    }
    QMetaProperty p = meta->property(id);
#ifndef QT_NO_DEBUG
    if (!p.isWritable())
        qWarning("%s::setProperty: Property \"%s\" invalid,"
                 " read-only or does not exist", metaObject()->className(), name);
#endif
    return p.write(this, value);
}