背景
deleteLater 是 QObject 類對象的成員函數,用于延遲删除一個 QObject 類對象,且對 QObject 類對象的删除推薦使用 deleteLater 而非 delete 。
deleteLater
①.概述
deleteLater 依賴于事件循環,調用 deleteLater 後本質是發送了一個 DeferrerDelete 事件,在事件循環進行中把對象删除。
②.代碼示例
demo = new QtClassDemo(this);
demo->deleteLater();
demo = nullptr;
deleteLater 和 delete
①.deleteLater 會在目前對象的所有事件處理完成後再删除對象
demo = new QtClassDemo(this);
demo->setObjectName("demo");qApp->postEvent(demo, new CustomEvent("hello"));
qApp->postEvent(demo, new CustomEvent("world"));demo->deleteLater();
demo = nullptr;
②.delete 則是立即删除對象,對象的既有事件不再處理
demo = new QtClassDemo(this);
demo->setObjectName("demo");qApp->postEvent(demo, new CustomEvent("hello"));
qApp->postEvent(demo, new CustomEvent("world"));delete demo;
demo = nullptr;
③.deleteLater 後依然可以通路和操作對象,直到再次回到事件循環
demo = new QtClassDemo(this);
demo->setObjectName("demo");demo->deleteLater();
qDebug() << demo->objectName();
demo = nullptr;
deleteLater 和 QSharedPointer
①.概述
智能指針可以傳入自定義的删除器,對于繼承自 QObject 的類對象可以傳入 deleteLater 。
②.代碼示例
QSharedPointer<QtClassDemo> demoClass(new QtClassDemo(this), &QObject::deleteLater);
deleteLater 和 moveToThread
①.概述
qDebug() << "主線程:"<< QThread::currentThread();
QThread * workThread = new QThread;demo = new QtClassDemo(nullptr);
demo->setObjectName("demo");
demo->moveToThread(workThread);
workThread->start();bool QtClassDemo::event(QEvent * event)
{
qDebug() << "事件處理線程:"<< QThread::currentThread() << event->type(); return QObject::event(event);
}
②.利用 deleteLater 進行資源清理
//工作對象工作完成,停止線程
QObject::connect(workObject,&WorkObject::workFinished,[&](){
workThread->quit();
workThread->wait();
});
//工作線程停止,删除工作對象
QObject::connect(workThread,&QThread::finished,workObject,&WorkObject::deleteLater );
//工作對象銷毀,删除工作線程
QObject::connect(workObject,&WorkObject::destroyed,workThread,&QThread::deleteLater );