ESP32 Forum

Posted: **Fri May 05, 2023 12:26 pm**

Hi,

I think this question has already been answered, because I think I read it a few days ago, but I swear I can't get to find the discussion anymore. So my question is, in the esp_mqtt component, when I register an event like this:

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esp_mqtt_client_register_event(client, MQTT_EVENT_CONNECTED, mqtt_connected_handler, mqtt_topic_bk);

being mqtt_topic_bk a pointer to a struct... how do I get in the event handler, the pointer to that struct back? Is it inside of:

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((esp_mqtt_event_handle_t *)event_data)->data

I mean... How is it structured? data is a pointer to? "Data associated with this event" https://docs.espressif.com/projects/esp ... tt_event_tThat means? Is it the data I passed when I registered the event or when it gets data from the broker (Looking at the examples provided, that seems to be what is happening). But then I dont get where does my event handler get the event_handler_arg

Posted: **Fri May 05, 2023 2:56 pm**

The first parameter of your event handling function is the void* event_handler_arg which receives the event_handler_arg value you provided upon registration of the event handler. If you pass in a "my_struct*" at registration, you can get it back in an event handling function

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void my_evt_handler_func(void *event_handler_arg, esp_event_base_t event_base, int32_t event_id, void *event_data)

via

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my_struct* p_my_struct = (my_struct*)event_handler_arg;

Posted: **Fri May 05, 2023 3:42 pm**

I see... I feel so stupid right now... I was looking for something that was literaly in front of me...
Thank you

ESP32 Forum

event_handler_arg in Esp_mqtt component. How do I access the arg from the handler?

event_handler_arg in Esp_mqtt component. How do I access the arg from the handler?

Re: event_handler_arg in Esp_mqtt component. How do I access the arg from the handler?

Re: event_handler_arg in Esp_mqtt component. How do I access the arg from the handler?