Breaking project into files: Confusion with Instantiated objects..

[Castingflame]

I have been breaking my project into .cpp and .h files. I am a bit confused about instances of objects.

For Instance (pun intended), If I wish to use the SoftwareSerial library in both my .ino main sketch and one of the .cpp files can I share one instance of the SoftwareSerial object? My head says yes, but I can't work out how to do it. I always end up with 'multiple definition of xyz' or ' was not declared in this scope' type errors.

**Example ** 1 instance of the SoftwareSerial object instantiated in hello.ino

// hello.ino

//INCLUDES
#include <SoftwareSerial.h>
#include "Arduino.h"
#include "world.h"

//DEFINES
//      VARIABLE		|AR. NUM.  |PIN NAME	|IC PIN	|FUNCTION
//-----------------------------------------------------------------------------------------------------------------------	
#define Soft_TXD        14          //PA1		17		Software Serial TXD
#define Soft_RXD        15          //PA2		18		Software Serial RXD


// INSTANTIATIONS
SoftwareSerial SoftSerial(Soft_RXD, Soft_TXD);    //RX, TX


void setup() {

	Serial.begin(9600);		// Software Serial start	
}

void loop()
{
	SoftSerial.print("Hello ");		// Print to softwareSerial
	world.Print("world!");			// Send to world class to print to SoftwareSerial
}

// world.h
#ifndef _WORLD_h
#define _WORLD_h

class worldclass
{
public:
	worldclass();
	void Print(String);
};
extern worldclass world;
#endif

// world.cpp
#include "Arduino.h"
#include "world.h"


worldclass::worldclass() {}


void worldclass::Print(String) {
	
	SoftSerial.print("world");
}



////////////////////////////////
worldclass world = worldclass();

RESULTS (which is to be expected)

world.cpp: 12:2: error: 'SoftSerial' was not declared in this scope
   SoftSerial.print("world")

I can 'fix' it by creating another instance of the SoftwareSerial in the world.cpp file but then, as far as I understand it, I will have two instances in memory. That just seems wrong and I feel I should be able to use just one.

I think it may be something to do with using Extern in the .cpp file but I can not seem to get it to work with an object instance, only variables.

[gfvalvo]

Pass a reference to the SoftwareSerial object (as a Stream &) into your class's constructor:

class worldclass {
  public:
    worldclass(Stream &str);
    void Print(String s);

  private:
    Stream &printStream;
};

worldclass::worldclass(Stream &str): printStream(str) {
}

void worldclass::Print(String s){
  printStream.print(s);
}

[JiPe38]

An example with a pointer to the class. The instance is created / deleted dynamically.

// hello.ino

#include "world.h"

Worldclass * world ;

void setup() {
  Serial.begin(115200);   // Software Serial start  
}

void loop()
{
  world = new Worldclass () ;
  Serial.print("Hello ");   // Print to Serial
  world->Print("world!");      // Send to world class to print to SoftwareSerial
  Serial.println () ;
  delete world ;
}

// world.h
#ifndef _WORLD_h
#define _WORLD_h

class Worldclass
{
public:
	Worldclass();
	void Print(String);
};
#endif

// world.cpp
#include "Arduino.h"
#include "world.h"


Worldclass::Worldclass() {}

void Worldclass::Print(String) {
	Serial.print("world");
}

[Castingflame]

Thanks guys I'll give the suggestions a go when I have finished creating the rest of my latest new .cpp class.

[Perehama]

You will want to come to a very clear understanding of what the following terms mean: define, declare, instantiate, initialize and assign along with storage classes, auto, static, extern and register and type qualifiers, const, volatile, restrict and _Atomic. It's too much to include in a response, so I'm giving you some google homework. I will be honest with you, it's not intuitive. H files typically include declarations, but not definitions, while C, CPP and INO files typically include definitions. These terms can have subtle differences between variables and functions and classes.