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Input handlers

There are four types of input handlers:

• Global input handler. This unique handler will handle every changed settable properties for all nodes

bool globalInputHandler(const HomieNode& node, const String& property, const HomieRange& range, const String& value) {

}

void setup() {
  Homie.setGlobalInputHandler(globalInputHandler); // before Homie.setup()
  // ...
}

• Node input handlers. This handler will handle every changed settable properties of a specific node

bool nodeInputHandler(const String& property, const HomieRange& range, const String& value) {

}

HomieNode node("id", "type", nodeInputHandler);

• Virtual callback from node input handler

You can create your own class derived from HomieNode that implements the virtual method bool HomieNode::handleInput(const String& property, const String& value). The default node input handler then automatically calls your callback.

class RelaisNode : public HomieNode {
 public:
    RelaisNode(): HomieNode("Relais", "switch8");

 protected:
  virtual bool handleInput(const String& property, const HomieRange& range, const String& value) {

  }
};

• Property input handlers. This handler will handle changes for a specific settable property of a specific node

bool propertyInputHandler(const HomieRange& range, const String& value) {

}

HomieNode node("id", "type");

void setup() {
  node.advertise("property").settable(propertyInputHandler); // before Homie.setup()
  // ...
}

You can see that input handlers return a boolean. An input handler can decide whether or not it handled the message and want to propagate it down to other input handlers. If an input handler returns true, the propagation is stopped, if it returns false, the propagation continues. The order of propagation is global handler → node handler → property handler.

For example, imagine you defined three input handlers: the global one, the node one, and the property one. If the global input handler returns false, the node input handler will be called. If the node input handler returns true, the propagation is stopped and the property input handler won't be called. You can think of it as middlewares.

Warning

Homie uses ESPAsyncTCP for network communication that make uses of asynchronous callback from the ESP8266 framework for incoming network packets. Thus the input handler runs in a different task than the loopHandler(). So keep in mind that the network task may interrupt your loop at any time.