翻译I have my first Qt application in development. It's a desktop client for site messaging.
Qt documentation says that i need to have only one instance of QNetworkAccessManager accross application. But i also read that using of singletons with Qt isn't a good idea. How i can make one instance of QNetworkAccessManager across app?
Another question is how to properly connect slots while i call ApiHandler functions from other classes?
For example i have ExampleApi class which uses functions of ApiHandler, in updateMessageList slot messagesListUpdated should be connected after request finished to update message list in view, but it never called.
ExampleApi.h
... #include "apihandler.h" class ExampleApi : public QObject { Q_OBJECT public: explicit ExampleApi(QObject *parent = 0); void updateMessagesList(); signals: public slots: void messagesListUpdated(QNetworkReply* reply); };ExampleApi.cpp
ExampleApi::ExampleApi(QObject *parent) : QObject(parent) { } void ExampleApi::updateMessagesList() { QMap<QString, QString> m; m["user_id"] = ConfigParser::settings.value(USER_ID).toString(); QNetworkAccessManager nam; ApiHandler a(&nam); // Connect a slot connect(a.getManager(), SIGNAL(finished(QNetworkReply*)), this, SLOT(messagesListUpdated(QNetworkReply*))); a.makeRequest("messages.get", m); } void ExampleApi::messagesListUpdated(QNetworkReply* reply) { QJsonDocument j = QJsonDocument::fromJson(reply->readAll()); QJsonObject getjson = j.object(); qDebug() << "ExampleApi::messagesListUpdated()" << getjson; reply->deleteLater(); // ... }ApiHandler.h
class ApiHandler : public QObject { Q_OBJECT public: explicit ApiHandler(QNetworkAccessManager *nam, QObject *parent = 0); ~ApiHandler(); QNetworkReply* makeRequest(QString method, QMap<QString, QString> parameters); QNetworkAccessManager* getManager(); private: QUrl buildCall(QString method, QMap<QString, QString> parameters); QNetworkAccessManager* manager; signals: public slots: void replyFinished(QNetworkReply* reply); void slotReadyRead(); void slotError(QNetworkReply::NetworkError error); void slotSslErrors(QList<QSslError> errorList); };ApiHandler.cpp
#include "apihandler.h" ApiHandler::ApiHandler(QNetworkAccessManager *nam, QObject *parent) : QObject(parent), manager(nam) { Q_ASSERT(manager); } ApiHandler::~ApiHandler() { manager->deleteLater(); } QUrl ApiHandler::buildCall(QString method, QMap<QString, QString> parameters) { QUrl url = QUrl(API_URL + method); QUrlQuery query; ConfigParser c; // Append first access_token query.addQueryItem("access_token", c.settings.value(ACCESS_TOKEN_KEY).toString()); if (!parameters.isEmpty()) { QMapIterator<QString, QString> i(parameters); while (i.hasNext()) { i.next(); query.addQueryItem(i.key(), i.value()); } } url.setQuery(query.query()); return url; } QNetworkReply* ApiHandler::makeRequest(QString method, QMap<QString, QString> parameters) { QUrl url = this->buildCall(method, parameters); //qDebug() << "ApiHandler::makeRequest: " << url; connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*))); QNetworkRequest request; request.setUrl(url); request.setRawHeader("User-Agent", "Site-Client"); QNetworkReply *reply = manager->get(request); connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead())); connect(reply, SIGNAL(error(QNetworkReply::NetworkError)), this, SLOT(slotError(QNetworkReply::NetworkError))); connect(reply, SIGNAL(sslErrors(QList<QSslError>)), this, SLOT(slotSslErrors(QList<QSslError>))); return reply; } void ApiHandler::replyFinished(QNetworkReply* reply) { qDebug() << "ApiHandler::replyFinished:" << reply->url(); QJsonDocument j = QJsonDocument::fromJson(reply->readAll()); if (j.isEmpty()) { // throw error qDebug("ApiHandler::replyFinished(...) j.isEmpty :("); } else { qDebug() << "ApiHandler::replyFinished(...)" << j; } reply->deleteLater(); } void ApiHandler::slotReadyRead() { //qDebug("slotReadyRead"); } void ApiHandler::slotError(QNetworkReply::NetworkError error) { qWarning() << "raised error:" << error; } void ApiHandler::slotSslErrors(QList<QSslError> errorList) { qWarning() << "raised sslErrors" << errorList; } QNetworkAccessManager* ApiHandler::getManager() { return this->manager; }