Initialize object from .cpp file

Question

Quick question, can I initialize an object (found uninitialized inside .h file) from inside a method inside a .cpp file?

I tried with "obj = Object ();" but it doesn't work from within the method, it only works if I put it inside the file.h

EX: file.h
Object obj;

EX: file.cpp
void XXXX::myFun(int param) {
obj = Object(param)
}

Answer 1

So you're also programming Arduino, I understand now why you didn't care to know it 😅
I think I found a solution which is replacing OtherClass a; by OtherClass* a;
Then, replacing a = OtherClass(0); by a = new OtherClass(0);
With this, all works fine but don't forget to apply the same corections for b

Answer 2

Listen, I developed once a library for arduino (deleted now) and I had this problem and beside the new operator I've found two solutions :
1_Inspired from Kotlin : replace the OtherClass constructor by OtherClass::OtherClass() {}, then make :
OtherClass::init(int param) {}, next : OtherClass a; and finally in the begin() method replace a = OtherClass(0) by a.init(0) (do the same for b)
2_Initialize a and b with a defult value when declaration (ex: OtherClass a = OtherClass(1)) then do what you want in the begin() method
After one of these solutions, c.a.fun() will work

Answer 3

Try to use instead : Object obj() or Object obj = new Object()

Answer 4

Wrong and wrong

Answer 5

One minute, please reformulate your question, you want to program a module or execute a simple code ?

Answer 6

I'm building a library, in the header file there are two uninitialized objects, in the cpp file I use a "begin()" method to initialize the two objects in the header file, only it's not as simple as I thought since I just write:

a = Object(param);

it gives me an error

Answer 7

the problem is just that. If I write

Object a = Object(param);

inside the header file, the code compiles perfectly.

Answer 8

Listen, I will make a tutorial about module programming in C++ because I did it too but without the files, I can't understand your code, but you may check this article which will help you :
https://www.arduino.cc/en/Hacking/libraryTutorial
It's a C++ library making tutorial for Arduino, if you find these functions : digitalWrite, delay and pinMode, just understand that they are simple functions, but if you follow me, I'll be able to explain what are these functions and what is Arduino

Answer 9

I don't care what is arduino, I care if and how an obj can be initialized from within a method in cpp file

Answer 10

Please, give me the files

Answer 11

And from where Object comes ?

Answer 12

I don't understand, do I have to use a pointer? Should I use ClassName::Obj? What can I do ?

Answer 13

//XXXX.h
#ifndef XXXX_h
#define XXXX_h
#include "Object.h"
Object obj;
void myFun(int);
#endif

//XXXX.cpp
#include "Object.h"
#include "XXXX.h"
void myFun(int param) {
obj = Object(param);
}

//main.cpp
#include <iostream.h>
#include "XXXX.h"
int main() {
begin(5);
return 0;
}

I think this is what you want

Answer 14

//Class.h#
#ifndef CLASS_H
#define CLASS_H

#include "OtherClass.h"

class Class {

public:
Class();
void begin();

OtherClass a;
OtherClass b;
};
#endif

//Class.cpp#
#include "Class.h"

Class::Class() {

}

void Class::begin() {
a = OtherClass(0);
b = OtherClass(0);
}

//OtherClass.h#
#ifndef OTHER_CLASS_H
#define OTHER_CLASS_H

class OtherClass {

public:
OtherClass(int param);
};
#endif

//OtherClass.cpp#
#include "OtherClass.h"

OtherClass::OtherClass(int param) {

}

Answer 15

This is code

Answer 16

Thank you but your code is correct, so what's the problem or the error ?

Answer 17

not compile

Answer 18

What's the error message ?

Answer 19

C:\Users\Mick\Documents\Arduino\libraries\Class\Class.cpp: In constructor 'Class::Class()':
C:\Users\Mick\Documents\Arduino\libraries\Class\Class.cpp:4:14: error: no matching function for call to 'OtherClass::OtherClass()'
Class::Class() {
^
In file included from C:\Users\Mick\Documents\Arduino\libraries\Class\Class.h:4:0,
from C:\Users\Mick\Documents\Arduino\libraries\Class\Class.cpp:1:
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:8:5: note: candidate: OtherClass::OtherClass(int)
OtherClass(int param);
^~~~~~~~~~
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:8:5: note: candidate expects 1 argument, 0 provided
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate: constexpr OtherClass::OtherClass(const OtherClass&)
class OtherClass {
^~~~~~~~~~
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate expects 1 argument, 0 provided
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate: constexpr OtherClass::OtherClass(OtherClass&&)
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate expects 1 argument, 0 provided
C:\Users\Mick\Documents\Arduino\libraries\Class\Class.cpp:4:14: error: no matching function for call to 'OtherClass::OtherClass()'
Class::Class() {
^
In file included from C:\Users\Mick\Documents\Arduino\libraries\Class\Class.h:4:0,
from C:\Users\Mick\Documents\Arduino\libraries\Class\Class.cpp:1:
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:8:5: note: candidate: OtherClass::OtherClass(int)
OtherClass(int param);
^~~~~~~~~~
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:8:5: note: candidate expects 1 argument, 0 provided
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate: constexpr OtherClass::OtherClass(const OtherClass&)
class OtherClass {
^~~~~~~~~~
C:\Users\Mick\Docume

Answer 20

nts\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate expects 1 argument, 0 provided
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate: constexpr OtherClass::OtherClass(OtherClass&&)
C:\Users\Mick\Documents\Arduino\libraries\Class\OtherClass.h:5:7: note: candidate expects 1 argument, 0 provided