How to initialize a class of a class of a class ('=' - reference cannot be initialized )

[Enau]

I follow this guide to create classes loaded like usual variables, ie "my_class  class1(Param1, Param2,...);" with ''parametric constructor".

chapter "Passing Parameters to Constructor"

https://www.mql5.com/en/articles/351

my problem is that when i create a class3 of a class2 of a class1,  I can't give a default value of class2, in the constructor of class3, because class2 is ''passed as reference''.

Here is my situation:

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class class1
{
public:
 int                 m_num1;
//---

                     class1(int c_num1=99)
 {
  init_1(c_num1);
 }
 void                init_1(int i_num1)
 {
  m_num1=i_num1;
 }
//class1(void);
                    ~class1(void);
};
//---
class1 number1(30);
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
//class1 c_Klass1(33);
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class class2
{
public:
 class1                                 m_Klass1;
 int                 m_num2;
//---

                     class2(class1&c_Klass1,int c_num2=74)
 {
  init_2(c_Klass1,c_num2);
 }
 void                init_2(class1&i_Klass1,int i_num2)
 {
  m_Klass1=i_Klass1;
  m_num2=i_num2;
 }
//class2(void);
                    ~class2(void);
};
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class2 number2A(number1, 10);
class2 number2B(number1, 32);
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
//class2 c_Klass2(number1,73);
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class class3
{
public:
 class2                                 m_Klass2A;
 class2                                 m_Klass2B;
 int                 m_num3;
//---

                     class3(class2&c_Klass2A=??????,class2&c_Klass2B=??????,int c_num3=30)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< HOW TO INITIATE THIS
 {
  init_3(c_Klass2A,c_Klass2B,c_num3);
 }
 void                init_3(class2&i_Klass2A,class2&i_Klass2B,int i_num3)
 {
  m_Klass2A=i_Klass2A;
  m_Klass2B=i_Klass2B;
  m_num3=i_num3;
 }
//class3(void);
                    ~class3(void);
};
class3(number2A, number2B, 83);

[fxsaber]

class class2
{
public :
 class1                                 m_Klass1;
 int                  m_num2;
//---

 class2( void ) {}
                     
                     class2(class1&c_Klass1, int c_num2= 74 )
 {
  init_2(c_Klass1,c_num2);
 }
 void                 init_2(class1&i_Klass1, int i_num2)
 {
  m_Klass1=i_Klass1;
  m_num2=i_num2;
 }
//class2(void);
                    ~class2( void );
};
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class2 number2A(number1, 10);
class2 number2B(number1, 32);
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
//class2 c_Klass2(number1,73);
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class class3
{
public :
 class2                                 m_Klass2A;
 class2                                 m_Klass2B;
 int                  m_num3;
//---

                     class3(class2&c_Klass2A,class2&c_Klass2B, int c_num3= 30 )
 {
  init_3(c_Klass2A,c_Klass2B,c_num3);
 }
 void                 init_3(class2&i_Klass2A,class2&i_Klass2B, int i_num3)
 {
  m_Klass2A=i_Klass2A;
  m_Klass2B=i_Klass2B;
  m_num3=i_num3;
 }
//class3(void);
                    ~class3( void );
};

class3 TmpClass3(number2A, number2B, 83);

[Enau]

fxsaber:

Your code works. Now If I UNcomment the default constructor of class1, I get the error :

'class1' - ambiguous call to overloaded function with the same parameters 
could be one of 2 function(s) 
   class1::class1() 
   class1::class1(int)  
'class1' - ambiguous call to overloaded function with the same parameters 
could be one of 2 function(s) 
   class1::class1()    
   class1::class1(int)  
2 errors, 0 warnings     

How do I choose the constructor of class1, between

   class1::class1() 

and
   class1::class1(int)   ??

THis is the code which produces the error

class class1
{
public:
 int                 m_num1;
//---

                     class1(int c_num1=99)
 {
  init_1(c_num1);
 }
 void                init_1(int i_num1)
 {
  m_num1=i_num1;
 }
                        class1(void) {};////<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Now UN commented
                    ~class1(void) {};
};
//---
class1 number1(30);
//+------------------------------------------------------------------+
//| |
//+------------------------------------------------------------------+

//+------------------------------------------------------------------+
//| |
//+------------------------------------------------------------------+
class class2
{
public:
 class1                                 m_Klass1;
 int                 m_num2;
//---

                     class2(class1&c_Klass1,int c_num2=74)////<<<<<<<<<<<<<<<<<<problem here
 { 
  init_2(c_Klass1,c_num2);
 }
 void                init_2(class1&i_Klass1,int i_num2)
 {
  m_Klass1=i_Klass1;
  m_num2=i_num2;
 }
                     class2(void) {};
                    ~class2(void) {};
};
//+------------------------------------------------------------------+
//| |
//+------------------------------------------------------------------+
class2 number2A(number1,10);
class2 number2B(number1,32);
//+------------------------------------------------------------------+
//| |
//+------------------------------------------------------------------+

//+------------------------------------------------------------------+
//| |
//+------------------------------------------------------------------+
class class3
{
public:
 class2                                 m_Klass2A;
 class2                                 m_Klass2B;
 int                 m_num3;
//---

                     class3(class2&c_Klass2A,class2&c_Klass2B,int c_num3=30)
 {
  init_3(c_Klass2A,c_Klass2B,c_num3);
 }
 void                init_3(class2&i_Klass2A,class2&i_Klass2B,int i_num3)
 {
  m_Klass2A=i_Klass2A;
  m_Klass2B=i_Klass2B;
  m_num3=i_num3;
 }
                     class3(void) {};
                    ~class3(void) {};
};
//+------------------------------------------------------------------+
//| |
//+------------------------------------------------------------------+
class3 temp3(number2A,number2B,83);

[fxsaber]

Enau:

Your code works. Now If I UNcomment the default constructor of class1, I get the error :

Then you yourself.

[Dominik Egert]

You need your special constructor not to have a default input assigned to the input parameter.

If you need a default constructor, go like this:

class1() : c_num(99) {};

This is a default constructor with initialization.

The other taking input parameters are not default constructors. Do not use presets in them.