Sending a message to a Telegram bot

[jsulm]

@jenya7 said in Sending a message to a Telegram bot:

the next step - refering to sys_params.bot_api_key generates the error

As @JonB asked: how does the stack trace look like after crash?

"How can I do it global?" - why should it be global? Simply make bot a class member...

[JonB]

@jenya7
As @jsulm has just written for the seg fault.

TelegramBot bot;  
     bot = new TelegramBot ("my_api_key");  //is not allowed

Why do you think this is "not allowed"? What does the compiler error message tell you, I would guess it's pretty clear?

[jenya7]

@jsulm said in Sending a message to a Telegram bot:

@jenya7 said in Sending a message to a Telegram bot:

the next step - refering to sys_params.bot_api_key generates the error

As @JonB asked: how does the stack trace look like after crash?

"How can I do it global?" - why should it be global? Simply make bot a class member...

It stops in qstring.h at
inline bool QString::isEmpty()
const { return d->size == 0; }

[jsulm]

@jenya7 This not stack trace...

[jenya7]

@JonB said in Sending a message to a Telegram bot:

@jenya7
As @jsulm has just written for the seg fault.

TelegramBot bot;  
     bot = new TelegramBot ("my_api_key");  //is not allowed

Why do you think this is "not allowed"? What does the compiler error message tell you, I would guess it's pretty clear?

TelegramBot bot; //here - error: no matching constructor for initialization of 'TelegramBot'

bot = new TelegramBot ("my_api_key");

[jsulm]

@jenya7 Please learn C++!
Your TelegramBot class has no constructor without parameter!
Also, if you want to allocate TelegramBot on the heap then bot needs to be a pointer. All these are absolute basics.

TelegramBot *bot;  
bot = new TelegramBot ("my_api_key");

[JonB]

@jenya7 said in Sending a message to a Telegram bot:

It stops in qstring.h at
inline bool QString::isEmpty()
const { return d->size == 0; }

In addition to @jsulm's excellent points. We don't know the scope of your sys_params (probably "global", yuck, don't do that), and:

typedef struct
{
   //some fields
    QString bot_api_key;
}SYS_PARAMS;
SYS_PARAMS sys_params;

We don't know whether you have written anything to the "some fields", or written directly into sys_params.

[jenya7]

@jsulm said in Sending a message to a Telegram bot:

@jenya7 This not stack trace...

1 QString::isEmpty qstring.h 937 0x28bd8
2 telebot::telebot telebot.cpp 10 0x56040
3 __static_initialization_and_destruction_0 telebot.cpp
4 0x5652c 4 _GLOBAL__sub_I_telebot.cpp(void) telebot.cpp 69 0x56588
5 __libc_csu_init 0xaf61c
6 __libc_start_main libc-start.c 264 0xb5ab96ac
7 _start 0x1c5dc

[jenya7]

@jsulm said in Sending a message to a Telegram bot:

@jenya7 Please learn C++!
Your TelegramBot class has no constructor without parameter!
Also, if you want to allocate TelegramBot on the heap then bot needs to be a pointer. All these are absolute basics.

TelegramBot *bot;  
bot = new TelegramBot ("my_api_key");

Thank you.

[jenya7]

@JonB said in Sending a message to a Telegram bot:

@jenya7 said in Sending a message to a Telegram bot:

It stops in qstring.h at
inline bool QString::isEmpty()
const { return d->size == 0; }

In addition to @jsulm's excellent points. We don't know the scope of your sys_params (probably "global", yuck, don't do that), and:

typedef struct
{
   //some fields
    QString bot_api_key;
}SYS_PARAMS;
SYS_PARAMS sys_params;

We don't know whether you have written anything to the "some fields", or written directly into sys_params.

If I comment out the constructor stuff - I see all fields of sys_params perfectly initialized. The problem - it gets to
bot = new TelegramBot (sys_params.bot_api_key); before it's initialized. The constructor goes first and then goes sys_params initialization (SetupRun(); in main.cpp).

Why do I get to the constructor? I don't instantiate any telebot object at all in the code.
When I get to the constructor I see
sys_params.bot_api_key = <not accessible>
how can it be?

[JonB]

@jenya7 said in Sending a message to a Telegram bot:

I don't instantiate any telebot object at all in the code.

You do if you hit the constructor! And putting a breakpoint there would should you where you do so from.

[jenya7]

@JonB said in Sending a message to a Telegram bot:

@jenya7 said in Sending a message to a Telegram bot:

I don't instantiate any telebot object at all in the code.

You do if you hit the constructor! And putting a breakpoint there would should you where you do so from.

I see...
In telebot.h I have extern telebot m_telebot;
and in telebot.cpp telebot m_telebot;
in order to work with the object in other parts of the project.
And when I include telebot.h in main.cpp it gets initialized before sys_params is accessible.

[JonB]

@jenya7 said in Sending a message to a Telegram bot:

and in telebot.cpp telebot m_telebot;

Indeed, and that is where it will get instantiated.

Since you say it is m_telebot, is it a member variable in some class? Or is it a (mis-named) global? You will not want it to be a truly global variable. If its constructor requires accessing sys_params, and that needs initialising first at run time (e.g. the SetupRun(); you showed), it is your job to ensure sys_params has been initialised before a telebot is created.

[jenya7]

@JonB said in Sending a message to a Telegram bot:

@jenya7 said in Sending a message to a Telegram bot:

and in telebot.cpp telebot m_telebot;

Indeed, and that is where it will get instantiated.

Since you say it is m_telebot, is it a member variable in some class? Or is it a (mis-named) global? You will not want it to be a truly global variable. If its constructor requires accessing sys_params, and that needs initialising first at run time (e.g. the SetupRun(); you showed), it is your job to ensure sys_params has been initialised before a telebot is created.

I did it this way

telebot m_telebot;

static TelegramBot *bot = nullptr;

telebot::telebot(QObject *parent) : QObject(parent)
{
     //empty constructor 
}

void telebot::Start(QString api_key)
{
    bot = new TelegramBot(api_key);

    QObject::connect(bot, &TelegramBot::newMessage, this, &telebot::NewMessage);

    bot->startMessagePulling();
}

and in main.cpp

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

     MainWindow w;
     w.show();

     SetupRun();

    m_telebot.Start(sys_params.bot_api_key);
    m_telebot.SendText(sys_params.bot_chat_id, "Control board is connected");
}

This way it works good.

[JonB]

@jenya7
I am happy this is working for you. I will just say that you really ought not have your global telebot and TelegramBot * variables, things would be better if you used classes and instances in C++. But that's up to you. So long as telebot m_telebot is global you really ought not have that m_ prefix on the name, that is conventionally used (by some) for class member variables and will lead to confusion for anyone looking at your code, as I suspected.

[jsulm]

@jenya7 said in Sending a message to a Telegram bot:

This way it works good

But is really bad design as @JonB pointed out. Global variables should be avoided as much as possible...

[jenya7]

@JonB said in Sending a message to a Telegram bot:

@jenya7
I am happy this is working for you. I will just say that you really ought not have your global telebot and TelegramBot * variables, things would be better if you used classes and instances in C++. But that's up to you. So long as telebot m_telebot is global you really ought not have that m_ prefix on the name, that is conventionally used (by some) for class member variables and will lead to confusion for anyone looking at your code, as I suspected.

How should I use a telebot class in other modules without having it global?

[jenya7]

@jsulm said in Sending a message to a Telegram bot:

@jenya7 said in Sending a message to a Telegram bot:

This way it works good

But is really bad design as @JonB pointed out. Global variables should be avoided as much as possible...

I want to send messages

m_telebot.SendText(sys_params.bot_chat_id, "My messaged");

from other modules. how is it possible if m_telebot is not global?

[JonB]

@jenya7
I feared that you might ask this! I'm afraid I am not offering to teach/illustrate general C++ principles :) There are various alternatives, like singleton classes, even static class methods/variables, putting them into application state, doing it like QSqlDatabase does, .... I imagine that if you Google there are various suggestions proposed. I was just saying that nowadays having bald C-style global variables is "frowned upon. But also as I said, up to you.

I will make one comment. So long as this telebot m_telebot; is in your main.cpp, how do you intend to access it in other files/modules/classes anyway? I hope you're not intending to #include "main.h" in all your other .cpp files?

[jenya7]

@JonB said in Sending a message to a Telegram bot:

@jenya7
I feared that you might ask this! I'm afraid I am not offering to teach/illustrate general C++ principles :) There are various alternatives, like singleton classes, even static class methods/variables, putting them into application state, doing it like QSqlDatabase does, .... I imagine that if you Google there are various suggestions proposed. I was just saying that nowadays having bald C-style global variables is "frowned upon. But also as I said, up to you.

I will make one comment. So long as this telebot m_telebot; is in your main.cpp, how do you intend to access it in other files/modules/classes anyway? I hope you're not intending to #include "main.h" in all your other .cpp files?

extern telebot m_telebot; works pretty well.