how to declare and make objects inside another object's constructor?

Question

I am learning c++. I am tring to make a couple of objects inside another object but compiler is giving error - no matching function for call to 'Grass::Grass()' .

This is the header file of "world" object. In it I declared two "grass" objects :-

#ifndef WORLD_H
#define WORLD_H
#include "Grass.h"

using namespace std;

class World
{
public:
World();

private:
Grass g1;
Grass g2;
};

This is the cpp file of the "world" object. In the constructor I tried to make the "grass" objects but failed.

#include "World.h"
#include <iostream>

using namespace std;

World::World()
{
g1(200, 200);
g2(300, 200);
}

Andy · Accepted Answer · 2015-05-08 00:45:55Z

3

Your syntax is wrong. You're looking for what's known as a constructor initialization list. Try (assuming you've got the signature for the Grass constructor correct):

World::World() : 
    g1(200, 200),
    g2(300, 200)
{
    // Nothing 
}

answered May 8, 2015 at 0:45

Andy

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2 Comments

Andy Over a year ago

The constructor initialization list can be used for any member variable that requires construction upon initialization including primitive types.

vsoftco Over a year ago

@Andy and it should always be used if possible, even if the type has a default constructor, since instead of two calls (ctor + assignment operator) you only call the copy/move ctor.

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