我面临一个 C++ Qt4 Widget 的问题。此小部件用于将行添加到 SQLite 数据库中。以下是我面临的问题中使用的数据库表：
CREATE TABLE 'statuses' ('id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL UNIQUE , 'name' VARCHAR(50) NOT NULL UNIQUE , 'bgcolor' VARCHAR(6) NOT NULL DEFAULT ffffff, 'fgcolor' VARCHAR(6) NOT NULL DEFAULT 000000)
CREATE TABLE 'addresses' ('id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL UNIQUE , 'name' VARCHAR(50) NOT NULL UNIQUE , 'country' VARCHAR(25), 'town' VARCHAR(50), 'postal_code' VARCHAR(10), 'street' TEXT check(typeof('street') = 'text') , 'ref' VARCHAR(5) NOT NULL , 'status_id' INTEGER NOT NULL, FOREIGN KEY(status_id) REFERENCES statuses(id))
我编写的代码完全遵循 Qt 教程SQL WidgetMapper，如下所示：
CreateAddressDialog::CreateAddressDialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::CreateAddressDialog)
{
ui->setupUi(this);
/* Set up "buddies" */
ui->nameLabel->setBuddy(ui->nameLineEdit);
ui->refLabel->setBuddy(ui->refLineEdit);
ui->townLabel->setBuddy(ui->townLineEdit);
ui->streetLabel->setBuddy(ui->streetLineEdit);
ui->countryLabel->setBuddy(ui->countryLineEdit);
ui->postalCodeLabel->setBuddy(ui->postalCodeLineEdit);
ui->statusLabel->setBuddy(ui->statusCB);
/* Set up status model */
ui->statusCB->clear();
statusModel = new QSqlRelationalTableModel(this, backbone::instance()->db);
statusModel->setEditStrategy(QSqlTableModel::OnManualSubmit);
statusModel->setTable("addresses");
int statusFieldId = statusModel->fieldIndex("status_id");
/***** Warning: after next instruction fieldIndex('status_id') will return -1. */
statusModel->setRelation(statusFieldId,QSqlRelation("statuses", "id", "name"));
statusModel->select();
relModel = statusModel->relationModel(statusFieldId);
ui->statusCB->setModel(relModel);
ui->statusCB->setModelColumn(relModel->fieldIndex("name"));
mapper = new QDataWidgetMapper(this);
mapper->setItemDelegate(new QSqlRelationalDelegate(this));
mapper->setModel(statusModel);
mapper->addMapping(ui->refLineEdit, statusModel->fieldIndex("ref"));
mapper->addMapping(ui->nameLineEdit, statusModel->fieldIndex("name"));
mapper->addMapping(ui->statusCB, statusFieldId);
}
提交过程很简单，如下所示：
void CreateAddressDialog::accept()
{
if(ui->nameLineEdit->text().length() < 5){
QMessageBox::critical(0, tr("Error"),tr("The name must be at least 5 characters long."), QMessageBox::Cancel);
return;
}else if(ui->refLineEdit->text().length() > 10){
QMessageBox::critical(0, tr("Error"),tr("The reference may not be more than 10 characters long."), QMessageBox::Cancel);
return;
}else if(ui->statusCB->currentIndex() < 0){
QMessageBox::critical(0, tr("Error"),tr("The item must have a status."), QMessageBox::Cancel);
return;
}
qDebug() << mapper->submit();
this->close();
}
问题是 mapper->submit() 失败（显示“false”）。如果我调用模型的 lastError，则没有任何显示。映射到此映射器的字段是表的必填字段（id 除外，因为它被标记为自动增量）。
非常感谢任何帮助，因为我真的不明白（而且似乎无法找出）为什么这个小部件没有向数据库添加任何内容。让我提一下，我用标准的 SQLite 数据库查看器检查了 SQLite 数据库的内容。
PS：您可以在https://code.google.com/p/invensile/source/browse/#svn%2Ftrunk浏览完整代码以供参考
提前致谢！