General and Desktop

I am writing graphql client framework for Qt-Qml You can find it here.

for completeness for anyone else getting this error I had the realtimeDataSlot() declared under public in the .h file and it should have been in the private slots:

@JonB said in converting from float or double to QString results in output being 0: Warning: The QString content may only contain valid numerical characters which includes the plus/minus sign, the character e used in scientific notation, and the decimal point. Including the unit or additional characters leads to a conversion error. In which case RTFM is the rule of the day! but I'm lazy.

Hi and welcome to devnet, Not a formal answer as I am not involved in that part but: status is for the module status so whether in belongs to the essential set, add-on, technical preview, etc depends means that the listed modules are mandatory to build recommends means that additional features can be enabled if listed modules are present as for priority, I don't know.

It is somehow reasonable to use QSharedPointer here. Most of the time it is not a good idea to use raw pointers (in modern C++). Someone has to manage the memory. Most of the time it will just work in Qt because most of the time Qt objects have a parent which will handle deletion of children when destroyed. If those pointers only live because they are inside a container, the container should use a smart pointer (I'd prefer std::shared_ptr over QSharedPointer, but that's a different topic). There is an easy solution to the problem of connecting when using a shared pointer inside the map. connect() expects a raw pointer. For a smart pointer you get its raw pointer by calling get, i.e. objectsList[obj1].get(). This is the whole trick here. @Linhares said in [SOLVED] Signals and slots as parameters: addConnection("object1", "signal1", "object2", "slot1"); This approach will not work immediately. Once you get your connect() to compile it will tell you at runtime that the signal and slot could not be found. Certainly, you have to use the old connect syntax. The string needs to include the argument types, like "signal1(int)" or "slot1()". Or has that changed at some point?

Turned out an event loop was needed to make QModbus work. I had no idea. Connecting a timer to a method to read registers worked connect(&m_timer, &QTimer::timeout, this, &ModbusController::readInputRegisters);

@jsulm Now I use Modbus TCP Client without threads and everything works.

@Christian-Ehrlicher @jsulm Thanks for all suggestions and helps. I rewrite my code and now don't use thread to Modbus TCP Client, and everything works .... Only I have thinking why when I plug out ethernet from my PC the state does not change from Connected to Disconnected ? It change only when I turn off server... void ClientTicketMach::onModbusStateChanged(int state) { if (state == QModbusDevice::UnconnectedState){ qDebug() <<"Modbus TCP Client Disconnected"; tim_reconnect.start(10000); tim_reading_inputRegisters.stop(); emit modbusTCPClientConnectedState(true); } else if (state == QModbusDevice::ConnectedState){ qDebug() <<"Modbus TCP Client Connected"; tim_reading_inputRegisters.start(1000); emit modbusTCPClientConnectedState(false); } else if (state == QModbusDevice::ConnectingState){ qDebug() << "Modbus TCP Client Connecting"; emit modbusTCPClientConnectedState(true); } }

@Roberrt said in How to post request on Qt?: it does use OpenSSL by default It uses SSL for https URLs. http does not require SSL. To be able to access https URLs in your app you will also need to deploy OpenSSL libraries with your app. Qt already provides them.

@SGaist it worked, thank you for helping, it probably saved me hours...

Hi, You are missing #include "ui_MainWindow.h" in your test.cpp file. Out of curiosity, why are you creating a new file for that method ? You are making your codebase more complex for no benefit.

@astoffregen said in SQLDatabase query creates heap error: Did you know a good guide on how to include external libs/dlls in a visual studio c++ qt project? Don't do it by yourself but use qmake or cmake and let them handle this for you.

@jsulm the data that is sent is in the form of a char array, example, char message[] = "message here"; I use QString because before I was using std::string and I was getting errors when trying to submit that to the line edit, I think conversion type errors, using a QString removed that error and thus I just stuck with it. edit: oh it is working now, I feel like we didnt change anything though and we were just going through debug statements

not able to spontaneously receive "state changed" means you must implement "polling". that's what it is called. Polling is a necessary evil of event driven architectures when the device is, as you say, not sending status changes, but polling is usually hidden from the user by the framework. You need to decide with what resolution/time-interval to poll the device and implement it using the timer, not a thread. threading complicates things and is unnecessary. if you are truly convinced taht you must constantly poll (as fast as the cpu clock allows for) then accept that qt is not the correct framework for your task, as pegging the cpu will create real UI latency problems. Qt is designed for UI applications, not real-time processing.

@Ramkumar-Mohan said in Can't update Grid Layout: how to remove the deleted data widget Using https://doc.qt.io/qt-6/qgridlayout.html#takeAt for example. Or https://doc.qt.io/qt-6/qlayout.html#removeWidget