Cannot instantiate a parameterized object inside of another class

Question

I'm having troubles understanding the inner workings of classes and such.

I have a class called Attributes that contains parameters. In my .ino, I can simply instantiate an object with Attributes greenBark(1, 2); and everything is hunkey dorey.

Problem: Now I need to create a Attributes object in my other class, called Tree. I figured out if my constructor doesn't have parameters, I can create an object within another class just fine. However, my attributes class constructor has parameters. When I try to create an parameterized object within another class, the compiler tosses an error. How can I create an attributes object within my tree class? I'm sorry if I got some of these terms mixed up, I'm trying to keep up!

Here are my current files (made for this example:)

The .ino file

#include "attributes.h"
#include "tree.h"
Attributes greenBark(1, 2);
void setup()
{
 Serial.begin(9600);
}
void loop()
{
 greenBark.printAttributes();
}

attributes.cpp

#include "attributes.h"

Attributes::Attributes(int size, int texture)
{
 _size = size;
 _texture = texture; 
}
void Attributes::printAttributes()
{
 Serial.print("GreenBark Attributes: ");
 Serial.print("Size = ");
 Serial.print(_size);
 Serial.print(" Texure = ");
 Serial.print(_texture);
 Serial.println();
}

attributes.h

#pragma once
#include <Arduino.h>
class Attributes
{
 public:
 Attributes(int size, int texture); // constructor 
 void printAttributes(); // method
 private:
 int _size = 0;
 int _texture = 0;
};

tree.cpp

#include "attributes.h"
#include "tree.h"
Tree::Tree()
{
}

tree.h

#pragma once
#include <Arduino.h>
#include "attributes.h"
class Tree
{
 public:
 
 Tree(); // constructor
 
 void makeTree(); // method
 // I want to create an attributes class object in my current class, so naturally I'd try to
 // create the object just like I did in my .ino sketch, but the below line doesn't work.
 
 //Attributes redBark(1, 2);
 private: 
};

The error provided is this:

In file included from C:\Users\ajrob\Dropbox\Projects\Electronics\Arduino Sketchbook\ParameterizedConstructor\ParameterizedConstructor.ino:2:0:
C:\Users\ajrob\Dropbox\Projects\Electronics\Arduino Sketchbook\ParameterizedConstructor\tree.h:16:24: error: expected identifier before numeric constant
 Attributes redBark(1, 2);
 ^
C:\Users\ajrob\Dropbox\Projects\Electronics\Arduino Sketchbook\ParameterizedConstructor\tree.h:16:24: error: expected ',' or '...' before numeric constant
In file included from C:\Users\ajrob\Dropbox\Projects\Electronics\Arduino Sketchbook\ParameterizedConstructor\tree.cpp:2:0:
C:\Users\ajrob\Dropbox\Projects\Electronics\Arduino Sketchbook\ParameterizedConstructor\tree.h:16:24: error: expected identifier before numeric constant
 Attributes redBark(1, 2);
 ^
C:\Users\ajrob\Dropbox\Projects\Electronics\Arduino Sketchbook\ParameterizedConstructor\tree.h:16:24: error: expected ',' or '...' before numeric constant
exit status 1
Compilation error: expected identifier before numeric constant

• Juraj: en.cppreference.com/w/cpp/language/constructor
• AJ_Smoothie: @Juraj I read that page over a few times understanding what I could and I'm not seeing how it helps my situation
• jsotola: I don't understand much of it either, so I tried Attributes redBark {1, 2}; and it did not throw an error ... I have no idea if it does what you are expecting ... Attributes redBark {1}; and Attributes redBark {1, 2, 3}; both throw an error, so it might be what you want
• jsotola: @AJ_Smoothie your post is not Arduino specific, and really is a general programming question ... it belongs at stackoverflow.com/questions
• AJ_Smoothie: @jsotola I tried the braces in my actual code (the parameters are input pins and default pin states) and it worked out just great. Thank you

Answer 1

I see two options here:

You might follow jsotola's comment and initialize redBark with braces:

Attributes redBark{1, 2};

For some reason, the syntax with parentheses is not allowed when initializing an object in a class declaration, but the syntax with braces is OK.

The other option is to initialize redBark in the Tree's constructor (and not in the class declaration) using an initializer list:

// In the class declaration:
Attributes redBark;
// The constructor:
Tree::Tree() : redBark(1, 2) {}

• AJ_Smoothie: Using the curly braces worked out just fine! Thank you!