Declaring variables outside of class in .h file for use in int function in .cpp

Projects Programming
1

Hi all,

I have a .cpp file that has

void function{
}
void function {
}
void function {
}
int function {
/* GET OR STORE THE HTTPS CODE */
int storeHttpsCode(long code) {
  if (code == 201) { //if we are to store the code
    result = code;
    Serial.println("201 Code");
    Serial.println(result);
  }
  else if (code == 1) { //if we are to return the code
    Serial.println("Return Code");
    Serial.println(result);
    return result; //return the code
    code = NULL; //clear the https code
  }
}

In my .h file I currently have:

#ifndef MyLibrary_h
#define MyLibrary_h

#include "Arduino.h"

int storeHttpsCode(long code);
long result;

class classname
{
  public:
    variable
    variable
    void function
  private:
};

#endif

But it doesn't like a variable being declared outside the class for the int function.

Does anyone know how to successfully initialize a variable for an int function outside a class?

Any help would be much appreciated!

Thanks,

Zeb

2

you should have posted the error

you shouldn't define variables, "result", in .h files because if the .h file is included in more than one other .cpp/.ino file there is an error because the definition is redundant.

3

Hi gcjr, thanks for your help! Unfortunately there is no "error" as such it just says it "couldn't compile".

So where do I initialize the variable "long result" for use in the .cpp file? (in an int function)

Thanks again,

Zeb

4

Sorry there is an error, here it is:

sketch\ESP32-testcode.ino.cpp.o:(.bss.result+0x0): multiple definition of `result'
sketch\testcode.cpp.o:(.bss.result+0x0): first defined here
collect2.exe: error: ld returned 1 exit status
Multiple libraries were found for "Adafruit_SSD1306.h"
 Used: C:\Users\E543-PC\Documents\Arduino\libraries\Adafruit_SSD1306
 Not used: C:\Users\E543-PC\Documents\Arduino\libraries\arduino_37042
Multiple libraries were found for "WiFi.h"
 Used: C:\Users\E543-PC\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.4\libraries\WiFi
 Not used: C:\Program Files (x86)\Arduino\libraries\WiFi
exit status 1
Error compiling for board ESP32 Dev Module.

Apologies,

Zeb

5

this can't work

void function{
}
void function {
}
void function {
}

nor this:

public:
variable
variable
void function
private:

on the other hand, the error message might show another problem.

So either

  • post your complete project, including all files and links to all used libraries. You can ZIP and post your files. or
  • make a minimum sketch which shows the problem - and again - post the full project
6

Hi all,

Sorry, I tried to simplify it to much!

I have written a very small piece of code.

.ino:

#include "TestCode.h"

long statusCode = 201;
testCode testcode;

void setup() {
  Serial.begin(115200);
}

void loop() {
  testcode.generateCode(statusCode);
  long httpsCode = storeHttpsCode(1);
  Serial.println("HTTPS Code Main Loop");
  Serial.println(httpsCode);
  if (httpsCode == 201) {
    Serial.println("dequeueing");
  }
  delay(1000);
}

.cpp

#include "Arduino.h"
#include "TestCode.h"

void testCode::generateCode(long statusCode) {
  switch (statusCode)
  {
    case 200:
      {
        Serial.println("Request succeeded");
        Serial.println("======================================================");
        break;
      }
    case 201:
      {
        Serial.println("New object created");
        Serial.println("======================================================");
        storeHttpsCode(201);
        break;
      }
    case 400:
      {
        Serial.println("Invalid request");
        Serial.println("======================================================");
        break;
      }
  }
}

/* GET OR STORE THE HTTPS CODE */
int storeHttpsCode(long code) {
  if (code == 201) { //if we are to store the code
    result = code;
    Serial.println("201 Code");
    Serial.println(result);
  }
  else if (code == 1) { //if we are to return the code
    Serial.println("Return Code");
    Serial.println(result);
    return result; //return the code
    code = NULL; //clear the https code
  }
}

.h

#ifndef TestCode_h
#define TestCode_h

#include "Arduino.h"

int storeHttpsCode (long code);
long result;

class testCode
{
  public:
    void generateCode(long statusCode);
  private:
};

#endif

And my error is:

sketch\TestCode.cpp.o:(.bss.result+0x0): multiple definition of `result'
sketch\ESP32-Test-Code.ino.cpp.o:(.bss.result+0x0): first defined here
collect2.exe: error: ld returned 1 exit status
exit status 1
Error compiling for board ESP32 Dev Module.

Thank you and apologies,

Zeb

7

"result" should be defined in one file, either .cpp or ,ino.

it should be declared as extern in the .h

that .h should be included in any .cpp/.ino that uses variables or functions defined in a different .cpp/.ino

8

Sweet thanks :slight_smile:

9

Here is the full code for anyone with the same problem :slight_smile:

.ino

#include "TestCode.h"

long statusCode = 201;
testCode testcode;

void setup() {
  Serial.begin(115200);
}

void loop() {
  testcode.generateCode(statusCode);
  long httpsCode = testcode.storeHttpsCode(1);
  Serial.println("HTTPS Code Main Loop");
  Serial.println(httpsCode);
  if (httpsCode == 201) {
    Serial.println("dequeueing");
  }
  delay(1000);
}

.cpp

#include "Arduino.h"
#include "TestCode.h"

void testCode::generateCode(long statusCode) {
  switch (statusCode)
  {
    case 200:
      {
        Serial.println("Request succeeded");
        Serial.println("======================================================");
        break;
      }
    case 201:
      {
        Serial.println("New object created");
        Serial.println("======================================================");
        storeHttpsCode(201);
        break;
      }
    case 400:
      {
        Serial.println("Invalid request");
        Serial.println("======================================================");
        break;
      }
  }
}

/* GET OR STORE THE HTTPS CODE */
int testCode::storeHttpsCode(long code) {
  if (code == 201) { //if we are to store the code
    result = code;
    Serial.println("201 Code");
    Serial.println(result);
  }
  else if (code == 1) { //if we are to return the code
    Serial.println("Return Code");
    Serial.println(result);
    return result; //return the code
    code = NULL; //clear the https code
  }
}

.h

#ifndef TestCode_h
#define TestCode_h

#include "Arduino.h"

class testCode
{
  public:
    void generateCode(long statusCode);
    int storeHttpsCode (long code);
    long result;
  private:
};

#endif

Thanks very much,

Zeb