Generic Custom Component
========================

This integration can be used to create generic custom components in ESPHome
using the C++ (Arduino) API. This integration should be used in cases where
none of ESPHome's abstraction layers (for example the "sensor", "binary sensor",
"switch", etc concepts) work well for your integration.

Please first read :doc:`/components/sensor/custom` guide, the same principles apply here.

The example below is an example of a custom component that can do anything you want really.

.. code-block:: cpp

    #include "esphome.h"

    class MyCustomComponent : public Component {
     public:
      void setup() override {
        // This will be called once to set up the component
        // think of it as the setup() call in Arduino
        pinMode(5, INPUT);
        pinMode(6, OUTPUT);
      }
      void loop() override {
        // This will be called very often after setup time.
        // think of it as the loop() call in Arduino
        if (digitalRead(5)) {
          digitalWrite(6, HIGH);

          // You can also log messages
          ESP_LOGD("custom", "The GPIO pin 5 is HIGH!");
        }
      }
    };

(Store this file in your configuration directory, for example ``my_custom_component.h``)

And in YAML:

.. code-block:: yaml

    # Example configuration entry
    esphome:
      includes:
        - my_custom_component.h

    custom_component:
    - lambda: |-
        auto my_custom = new MyCustomComponent();
        return {my_custom};
      components:
      - id: my_custom_id 
      

Configuration variables:

- **lambda** (**Required**, :ref:`lambda <config-lambda>`): The lambda to run for instantiating the
  binary sensor(s).
- **components** (*Optional*, list): A list of components to initialize. The length here
  must equal the number of items in the ``return`` statement of the ``lambda``. This is useful
  if you need to give an ``id`` to the component you created.

See also :apiclass:`Component`.

Native API Custom Component
---------------------------

If you want to communicate directly with Home Assistant via the :doc:`native API </components/api>`
you can use the :apiclass:`CustomAPIDevice` class to declare services that can be executed from
Home Assistant, as well as starting services in Home Assistant.

.. code-block:: cpp

    #include "esphome.h"

    class MyCustomComponent : public Component, public CustomAPIDevice {
     public:
      void setup() override {
        // This will be called once to set up the component
        // think of it as the setup() call in Arduino
        pinMode(6, OUTPUT);

        // Declare a service "hello_world"
        //  - Service will be called "esphome.<NODE_NAME>_hello_world" in Home Assistant.
        //  - The service has no arguments
        //  - The function on_hello_world declared below will attached to the service.
        register_service(&MyCustomComponent::on_hello_world, "hello_world");

        // Declare a second service "start_washer_cycle"
        //  - Service will be called "esphome.<NODE_NAME>_start_washer_cycle" in Home Assistant.
        //  - The service has three arguments (type inferred from method definition):
        //     - cycle_duration: integer
        //     - silent: boolean
        //     - string_argument: string
        //  - The function start_washer_cycle declared below will attached to the service.
        register_service(&MyCustomComponent::on_start_washer_cycle, "start_washer_cycle",
                         {"cycle_duration", "silent", "string_argument"});

        // Subscribe to a Home Assistant state "sensor.temperature"
        //  - Each time the ESP connects or Home Assistant updates the state, the function
        //    on_state_changed will be called
        //  - The state is a string - if you want to use it as an int you must parse it manually
        subscribe_homeassistant_state(&MyCustomComponent::on_state_changed, "sensor.temperature");
      }
      void on_hello_world() {
        ESP_LOGD("custom", "Hello World!");

        if (is_connected()) {
          // Example check to see if a client is connected
        }
      }
      void on_start_washer_cycle(int cycle_duration, bool silent, std::string string_argument) {
        ESP_LOGD("custom", "Starting washer cycle!");
        digitalWrite(8, HIGH);
        // do something with arguments

        // Call a homeassistant service
        call_homeassistant_service("homeassistant.service");
      }
      void on_state_changed(std::string state) {
        ESP_LOGD(TAG, "Temperature has changed to %s", state.c_str());
      }
    };

See also :apiclass:`api::CustomAPIDevice`.

MQTT Custom Component
---------------------

In many cases however components should communicate with other appliances using the network.
That's why there is :apiclass:`mqtt::CustomMQTTDevice`. It is a helper class to create
custom components that communicate using MQTT.

.. code-block:: cpp

    #include "esphome.h"

    class MyCustomComponent : public Component, public CustomMQTTDevice {
     public:
      void setup() override {
        // This will be called once to set up the component
        // think of it as the setup() call in Arduino
        pinMode(6, OUTPUT);

        subscribe("the/topic", &MyCustomComponent::on_message);

        // also supports JSON messages
        subscribe_json("the/json/topic", &MyCustomComponent::on_json_message);
      }
      void on_message(const std::string &payload) {
        if (payload == "ON") {
          digitalWrite(6, HIGH);
          publish("the/other/topic", "Hello World!");
        } else {
          digitalWrite(6, LOW);
          publish("the/other/topic", 42);
        }
      }
      void on_json_message(JsonObject root) {
        if (!root.containsKey("key"))
          return;

        int value = root["key"];
        // do something with Json Object

        // publish JSON using lambda syntax
        publish_json("the/other/json/topic", [=](JsonObject root2) {
          root2["key"] = "Hello World";
        });
      }
    };

See also :apiclass:`mqtt::CustomMQTTDevice`.

See Also
--------

- :ghedit:`Edit`