Doubt about accessing objects from split .cpp files

PlatformIO IDE
,
1

Hi,
For context:
I am playing around with the Cheap Yellow Display and LVGL+Squareline studio (LVGL for short) (trying to have some buttons for my HomeAssisyance instance.

With LVGL, the events are handled in a separate file called ui_events.cpp, extraction here:

/ This file was generated by SquareLine Studio
// SquareLine Studio version: SquareLine Studio 1.3.4
// LVGL version: 8.3.6
// Project name: COCINA

#include "ui.h"
#include <Arduino.h>
#include "config.h"

void CambiaHormo(lv_event_t * e)
{
	 
	  String Str4 = lv_label_get_text(ui_LabelHornoStatus1);
	  Serial.println( Str4 );
	  if (Str4== "OFF"){
		 lv_label_set_text(ui_LabelHornoStatus1, "ON");
		client.publish(horno_topic_cmnd, "ON");
		 Serial.print("ON");
	  }	  
	  if (Str4== "ON"){
		 lv_label_set_text(ui_LabelHornoStatus1, "OFF");
		client.publish(horno_topic_cmnd, "OFF");
		 Serial.print("OFF");
		 

	  }
}

But, the main part of the program is in the main.cpp file, in particular the wifi and Mqtt client
As you can read above, I am trying to publish in the MQTT broker once the button is clicked
So I read that I need to use the Keyword extern, and I used for the the follwoing lines in the main.cpp


extern WiFiClient espClient;
extern PubSubClient client(espClient);

But seem that that the compiler does not like it, as I receive the following error:

Compiling .pio\build\esp32dev\src\ui_events.cpp.o
In file included from src/main.cpp:5:
.pio/libdeps/esp32dev/TFT_eSPI/TFT_eSPI.h:973:8: warning: #warning >>>>------>> TOUCH_CS pin not defined, TFT_eSPI touch functions will not be available! [-Wcpp]
       #warning >>>>------>> TOUCH_CS pin not defined, TFT_eSPI touch functions will not be available!
        ^~~~~~~
src/ui_events.cpp: In function 'void CambiaHormo(lv_event_t*)':
src/ui_events.cpp:17:3: error: 'client' was not declared in this scope
   client.publish(horno_topic_cmnd, "ON");
   ^~~~~~
src/ui_events.cpp:17:3: note: suggested alternative: 'Client'
   client.publish(horno_topic_cmnd, "ON");
   ^~~~~~
   Client
src/ui_events.cpp:22:3: error: 'client' was not declared in this scope
   client.publish(horno_topic_cmnd, "OFF");
   ^~~~~~
src/ui_events.cpp:22:3: note: suggested alternative: 'Client'
   client.publish(horno_topic_cmnd, "OFF");
   ^~~~~~
   Client
src/main.cpp:30:37: warning: 'client' initialized and declared 'extern'
 extern PubSubClient client(espClient);

How can I access the espclient from the ui_events.cpp?
I guess that I can create flag variables and push the MQTT messages from the Main.cpp Loop() function… but I am wondering how to do splitting CPP files in VCS+PlatformnIO (for the sake of learning)

Thanks in advance for your help.

Regards

2

There is no need to add the constructor arguments in there, you just declare type and name of the variable. This should be just

extern PubSubClient client;