Function pointer for templated class method

Question

Hi everyone, I need a hand to solve this problem, I'm trying to create a function that allows me to call a class method passed as a parameter of the aforementioned function, only that once I compile the code I get this error:

src\main.cpp: In function 'void setup()':
src\main.cpp:38:37: error: invalid use of non-static member function 'void esp8266webserver::ESP8266WebServerTemplate<ServerType>::handleClient() [with ServerType = WiFiServer]'
38 | b25.handler.when_connected(server.handleClient);
| ~~~~~~~^~~~~~~~~~~~
In file included from ..\..\..\..\.platformio\packages\framework-arduinoespressif8266\libraries\ESP8266WebServer\src/ESP8266WebServer.h:340,
from src\main.cpp:4:
..\..\..\..\.platformio\packages\framework-arduinoespressif8266\libraries\ESP8266WebServer\src/ESP8266WebServer-impl.h:274:6: note: declared here
274 | void ESP8266WebServerTemplate<ServerType>::handleClient() {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Answer 1

I'm working with esp8266 board in PlatformIO in VSCode.

The line
b25.handler.when_connected(callbackfunction_t callback);

where

typedef void(*callbackfunction_t)(void);

Answer 2

I want to make the function pointer work without modifying the Esp8266WebServer class.

Answer 3

Yes, I'm making a similar one.

Answer 4

These lines together generate the error described above.

Answer 5

Mick ,

I don't know much about C++, but it'd be helpful if you link us to your code, like this:
https://sololearn.com/compiler-playground/c9XEgLk7ipsR/?ref=app
And, you can send us a screenshot of your error by sending us a link to your screenshot, which can be done using this website: https://imgur.com/

Answer 6

I hope you'll receive useful answers! I'm sorry I can't help you since I'm not a C++ developer.

Answer 7

code?

Answer 8

The method I am trying to pass as a parameter to this function is on line 109 of this library

handleClient();

link: https://github.com/esp8266/Arduino/blob/master/libraries/ESP8266WebServer/src/ESP8266WebServer.h

Answer 9

// orvibo_handler.h:
typedef void(*callbackfunction_t)(void);

// orvibo_handler.cpp:
void OrviboHandler::when_connected(callbackfunction_t callback) {
/* type: callbackfunction_t */ when_connected_function_pointer = callback;
}

Answer 10

Code that generate the error:

//main.cpp:

b25.handler.when_connected(server.handleClient);

Answer 11

without seeing the code you wrote or knowing how your project is set up or how your build system is configured, it's hard to tell where the problem is.

if it's your first time doing this, maybe start from simple tests and progress from that. have you tried compiling the test example first to see if your setup runs ok?

https://github.com/platformio/platform-espressif8266/blob/6ee41e971e3834667d41ffc6839eb392ec611ad5/examples/arduino-webserver/src/HelloServer.ino

Answer 12

Yes, the example test works great, I just have this problem. Like I can't use functionpointer_t with methods in classes that use the template keyword.

Answer 13

I didn't touch anything in the compiler configuration, I used the default settings for the esp8266 board with PlatformIO on VSCode

Answer 14

invalid use of non-static member function ...
maybe you first have to create an instance of the esp8266WebServer class and use that? just a wild guess ...

Answer 15

The project is not on github yet, I am evaluating whether to continue it or not. I created an instance of the class, it is called b25 using:

OrviboB25 b25;

statement.

Answer 16

There is nothing static about the OrviboB25 class

Answer 17

maybe some other members can give a more specific feedback. It's been years since I've played with these things, unfortunately.

have you visited this?
https://github.com/sandysound/orvibo-b25-server

Answer 18

If you had to store the pointer address of the server.handleClient(); method in a variable, how would you do it? Then call it inside the OrviboB25 class.

Answer 19

Have you tried creating an instance of the WiFiServer, then pointing to that instead of the base class?

Also, another link I found
https://github.com/xoseperez/espurna

Answer 20

What do you mean ?