Using ESPAsyncWebServer::on method in a function with variable argument

Q&A Forum › Using ESPAsyncWebServer::on method in a function with variable argument

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Selcuk Ozbayraktar asked 3 years ago

Hi Rui, Sara and colleagues,

I want to use server.on method in a function, with first argument being a string variable:

This works, as usual :

server.on( “/on”, HTTP_GET, [](AsyncWebServerRequest * request) { …..

But this one which I need, does not work :

String txt = “/on”;
server.on( txt, HTTP_GET, [](AsyncWebServerRequest * request) {……

I get following error message :

“no matching function for call to ‘AsyncWebServer::on(String&, WebRequestMethod, setup()::__lambda10)'”

How to get around, any idea?

I don’t want to repeat the same code for “/on1”, “/on2” … to control twelve or more relays.

Kind regards,

3 Answers

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Sara Santos Staff answered 3 years ago

Hi.

The best way to achieve that is to make requests with params. For example:

relay (GPIO 2) request to turn on: /update?output=2&state=1
relay (GPIO 2) request to turn off: /update?output=2&state=0
relay (GPIO 4) request to turn on: /update?output=4&state=1
relay (GPIO 4) request to turn off: /update?output=4&state=0

In your code, define the parameters of the URL:

const char* PARAM_INPUT_1 = "output";
const char* PARAM_INPUT_2 = "state";

Then, handle the web server with on single server.on() for every request. This will find the values passed on the parameters:

server.on("/update", HTTP_GET, [] (AsyncWebServerRequest *request) {
    String outputParamValue;
    String stateParamValue;
    // GET input1 value on <ESP_IP>/update?output=<outputParamValue>&state=<state>
    if (request->hasParam(PARAM_INPUT_1) && request->hasParam(PARAM_INPUT_2)) {
        outputParamValue= request->getParam(PARAM_INPUT_1)->value();
        stateParamValue= request->getParam(PARAM_INPUT_2)->value();
        //control the relay
        digitalWrite(outputParamValue.toInt(), stateParamValue.toInt());
    }
    else {
        outputParamValue = "No message sent";
        stateParamValue= "No message sent";
    }
    Serial.print("GPIO: ");
    Serial.print(outputParamValue);
    Serial.print(" - Set to: ");
    Serial.println(stateParamValue);
    request->send(200, "text/plain", "OK");
});

I hope this is clear. Let me know if you need further help.

Regards,
Sara

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Selcuk Ozbayraktar answered 3 years ago

Thanks a lot Sara, I will try this.
Kind regards,

Update for result : This has been resulted in a neat, easy to read and working code. Thanks again for your kind involvement.

BR.

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Sara Santos Staff answered 3 years ago

That’s great!
I’ll mark this issue as resolved.
If you need further help, you just need to open a new question in our forum.
Regards,
Sara