6.qsqlquerymodel源码分析

继承关系

qsqlquerymodel 继承与qabstracttablemodel

入口

负责填充数据

void QSqlQueryModel::setQuery(const QString &query, const QSqlDatabase &db) //无法配置绑定参数
void QSqlQueryModel::setQuery(const QSqlQuery &query) //非常友好，支持自定义query

浅析qsqlquery

你会发现提供的构造qsqlquery中如果
携带sql字符串语句则 if (!query.isEmpty()) q->exec(query);自动执行，具体请看qInit()
所以在使用qsqlquery的过程中如果传入sql语句则不用手动执行
否则就需要自己执行exec

QSqlQuery::QSqlQuery(QSqlDatabase db)
{d = QSqlQueryPrivate::shared_null();qInit(this, QString(), db);
}
QSqlQuery::QSqlQuery(const QString& query, QSqlDatabase db)
{d = QSqlQueryPrivate::shared_null();qInit(this, query, db);
}
//1.提供的数据库连接无效则获取默认的数据库，且未开启static void qInit(QSqlQuery *q, const QString& query, QSqlDatabase db)
{QSqlDatabase database = db;if (!database.isValid())database = QSqlDatabase::database(QLatin1String(QSqlDatabase::defaultConnection), false);if (database.isValid()) {*q = QSqlQuery(database.driver()->createResult());}if (!query.isEmpty())q->exec(query);
}

数据返回
sqlResult 是由不同的数据库驱动提供的

QSqlRecord QSqlQuery::record() const
{QSqlRecord rec = d->sqlResult->record();if (isValid()) {for (int i = 0; i < rec.count(); ++i)rec.setValue(i, value(i));}return rec;
}QVariant QSqlQuery::value(int index) const
{if (isActive() && isValid() && (index > -1))return d->sqlResult->data(index);qWarning("QSqlQuery::value: not positioned on a valid record");return QVariant();
}

而为什么qsqlquery可以使用qsqlresult的protected东西，虽然不是相互继承关系
但因为在qsqlresult中声明了qsqlquery为友元类，所以依旧能够使用
但是外部是无法使用的

所以外部提供的 没什么太大的作用

const QSqlResult * result() const

实际

qsqlquery.record() 第一行是表头
所以执行next再获取才是数据库里面查询结果的第一行数据

setquery分析

所以我们了解了qsqlquery的处理机制，
我们就明白在执行qsqlquerymodel 的setquery
就是将已经存在数据的query填充到querymodel 模型中供外部使用

void QSqlQueryModel::setQuery(const QSqlQuery &query)
{Q_D(QSqlQueryModel);beginResetModel();QSqlRecord newRec = query.record();bool columnsChanged = (newRec != d->rec);//设置列数if (d->colOffsets.size() != newRec.count() || columnsChanged)d->initColOffsets(newRec.count());d->bottom = QModelIndex(); //最后一行与最后一列的坐标d->error = QSqlError();d->query = query;d->rec = newRec; //表头d->atEnd = true; //最后一行吗//获取数据的方式是由下往上则//这个模型不支持这样子的queryif (query.isForwardOnly()) {d->error = QSqlError(QLatin1String("Forward-only queries ""cannot be used in a data model"),QString(), QSqlError::ConnectionError);endResetModel();return;}if (!query.isActive()) {d->error = query.lastError();endResetModel();return;}//query是否存在数据if (query.driver()->hasFeature(QSqlDriver::QuerySize) && d->query.size() > 0) {d->bottom = createIndex(d->query.size() - 1, d->rec.count() - 1);} else {d->bottom = createIndex(-1, d->rec.count() - 1);d->atEnd = false;}// fetchMore does the rowsInserted stuff for incremental modelsfetchMore();  //endResetModel();queryChange();
}

不难看出初始化数据需要这样子的闭合关系

beginResetModel();
//-----填充数据域
endResetModel();

刷新数据

void QSqlQueryModel::fetchMore(const QModelIndex &parent)
{Q_D(QSqlQueryModel);if (parent.isValid())return;//预先刷新多少行，QSQL_PREFETCH=255d->prefetch(qMax(d->bottom.row(), 0) + QSQL_PREFETCH);
}

//limit>255
void QSqlQueryModelPrivate::prefetch(int limit)
{Q_Q(QSqlQueryModel);// 如果确实是最后一行则不往下执行if (atEnd || limit <= bottom.row() || bottom.column() == -1)return;QModelIndex newBottom;const int oldBottomRow = qMax(bottom.row(), 0);// try to seek directly// 查看数据是否超过limit行，则新行先预加载到这里，//一个预加载操作if (query.seek(limit)) {newBottom = q->createIndex(limit, bottom.column());} else {// have to seek back to our old position for MS Accessint i = oldBottomRow;if (query.seek(i)) {while (query.next())++i;newBottom = q->createIndex(i, bottom.column());} else {// empty or invalid querynewBottom = q->createIndex(-1, bottom.column());}atEnd = true; // this is the end.}if (newBottom.row() >= 0 && newBottom.row() > bottom.row()) {q->beginInsertRows(QModelIndex(), bottom.row() + 1, newBottom.row());bottom = newBottom; //更新最后一行坐标q->endInsertRows();} else {bottom = newBottom;}
}

可以看到执行插入操作

beginInsertRows();
//插入操作作用域
endInsertRows();

扩展列或者移除列以及取别名

不难发现就是往rect表头管理的record里面加入一个新的qsqlfield

//批量增加列
bool QSqlQueryModel::insertColumns(int column, int count, const QModelIndex &parent)
{Q_D(QSqlQueryModel);if (count <= 0 || parent.isValid() || column < 0 || column > d->rec.count())return false;beginInsertColumns(parent, column, column + count - 1);for (int c = 0; c < count; ++c) {QSqlField field;field.setReadOnly(true);field.setGenerated(false);d->rec.insert(column, field);if (d->colOffsets.size() < d->rec.count()) {int nVal = d->colOffsets.isEmpty() ? 0 : d->colOffsets[d->colOffsets.size() - 1];d->colOffsets.append(nVal);Q_ASSERT(d->colOffsets.size() >= d->rec.count());}for (int i = column + 1; i < d->colOffsets.count(); ++i)++d->colOffsets[i];}endInsertColumns();return true;
}//批量删除列
bool QSqlQueryModel::removeColumns(int column, int count, const QModelIndex &parent)
{Q_D(QSqlQueryModel);if (count <= 0 || parent.isValid() || column < 0 || column >= d->rec.count())return false;beginRemoveColumns(parent, column, column + count - 1);int i;for (i = 0; i < count; ++i)d->rec.remove(column);for (i = column; i < d->colOffsets.count(); ++i)d->colOffsets[i] -= count;endRemoveColumns();return true;
}
//取别名
bool QSqlQueryModel::setHeaderData(int section, Qt::Orientation orientation,const QVariant &value, int role)
{Q_D(QSqlQueryModel);if (orientation != Qt::Horizontal || section < 0 || columnCount() <= section)return false;if (d->headers.size() <= section)d->headers.resize(qMax(section + 1, 16));d->headers[section][role] = value;emit headerDataChanged(orientation, section, section);return true;
}// 获取表头列名
QVariant QSqlQueryModel::headerData(int section, Qt::Orientation orientation, int role) const
{Q_D(const QSqlQueryModel);if (orientation == Qt::Horizontal) {QVariant val = d->headers.value(section).value(role);if (role == Qt::DisplayRole && !val.isValid())val = d->headers.value(section).value(Qt::EditRole);if (val.isValid())return val;if (role == Qt::DisplayRole && d->rec.count() > section && d->columnInQuery(section) != -1)return d->rec.fieldName(section);}return QAbstractItemModel::headerData(section, orientation, role);
}

读取数据与增减行

因为是数据库查询的，我觉的没必要setData
我们只需要控制我们的列就行了
比如，我们可以在前面加一列—到时候传入个checkbox或者单选框
在加入一个选择管理器就可以做到选择功能
最后就是一列多个按键，我们也可以通过多增加列进行

    model->insertColumns(0,1);model->setHeaderData(0,Qt::Horizontal,QString("选择"));

动态列的字段数据

 0: QSqlField("", , tableName: "(not specified)", generated: no, autoValue: false, readOnly: true) "" 

读取数据

//返回行数据
QSqlRecord QSqlQueryModel::record(int row) const
{Q_D(const QSqlQueryModel);if (row < 0)return d->rec;QSqlRecord rec = d->rec;for (int i = 0; i < rec.count(); ++i)rec.setValue(i, data(createIndex(row, i), Qt::EditRole));return rec;
}//表头数据
QSqlRecord QSqlQueryModel::record() const
{Q_D(const QSqlQueryModel);return d->rec;
}QVariant QSqlQueryModel::data(const QModelIndex &item, int role) const
{Q_D(const QSqlQueryModel);if (!item.isValid())return QVariant();QVariant v;if (role & ~(Qt::DisplayRole | Qt::EditRole))return v;// 非原来的 则直接返回， 就是调用insertColumns加的则直接返回if (!d->rec.isGenerated(item.column()))return v;//获取在query中实际位置QModelIndex dItem = indexInQuery(item);if (dItem.row() > d->bottom.row())const_cast<QSqlQueryModelPrivate *>(d)->prefetch(dItem.row());if (!d->query.seek(dItem.row())) {d->error = d->query.lastError();return v;}return d->query.value(dItem.column());
}QModelIndex QSqlQueryModel::indexInQuery(const QModelIndex &item) const
{Q_D(const QSqlQueryModel);int modelColumn = d->columnInQuery(item.column());if (modelColumn < 0)return QModelIndex();return createIndex(item.row(), modelColumn, item.internalPointer());
}int QSqlQueryModelPrivate::columnInQuery(int modelColumn) const
{if (modelColumn < 0 || modelColumn >= rec.count() || !rec.isGenerated(modelColumn) || modelColumn >= colOffsets.size())return -1;return modelColumn - colOffsets[modelColumn];
}// 提供给委托使用的， 如果设置
QHash<int, QByteArray> QSqlQueryModel::roleNames() const
{return QHash<int, QByteArray> {{ Qt::DisplayRole, QByteArrayLiteral("display") }};
}

而rolename有什么用？
主要用于在qml中可以使用属性名如model.name , model.display之类的

    void initializeConstructor(QQmlAdaptorModelEngineData *const data){QV4::ExecutionEngine *v4 = data->v4;QV4::Scope scope(v4);QV4::ScopedObject proto(scope, v4->newObject());proto->defineAccessorProperty(QStringLiteral("index"), get_index, nullptr);proto->defineAccessorProperty(QStringLiteral("hasModelChildren"), get_hasModelChildren, nullptr);QV4::ScopedProperty p(scope);typedef QHash<QByteArray, int>::const_iterator iterator;for (iterator it = roleNames.constBegin(), end = roleNames.constEnd(); it != end; ++it) {const int propertyId = propertyRoles.indexOf(it.value());const QByteArray &propertyName = it.key();QV4::ScopedString name(scope, v4->newString(QString::fromUtf8(propertyName)));QV4::ExecutionContext *global = v4->rootContext();QV4::ScopedFunctionObject g(scope, v4->memoryManager->allocate<QV4::IndexedBuiltinFunction>(global, propertyId, QQmlDMCachedModelData::get_property));QV4::ScopedFunctionObject s(scope, v4->memoryManager->allocate<QV4::IndexedBuiltinFunction>(global, propertyId, QQmlDMCachedModelData::set_property));p->setGetter(g);p->setSetter(s);proto->insertMember(name, p, QV4::Attr_Accessor|QV4::Attr_NotEnumerable|QV4::Attr_NotConfigurable);}prototype.set(v4, proto);}

下一章节：如何使用qsqlquerymodel 与 qtableview实现自定义表格