I get an error in the c ++ class constructor

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I get an error in the c ++ class constructor

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#1 by (1 votes)

1

#include <windows.h>
#include <stdio.h>
namespace textTDengine{
typedef const char* spr;
enum direction{up,down,left,right};
struct vector2{
    float x;
    float y;


    vector2(float x,float y){
        this->x = x;
        this->y = y;
        }

        COORD vector_to_coord(){
            COORD result;
            result.X = x;
            result.Y = y;
            return result;
        }


};


class object{
    spr sprite;

    vector2 position;

    direction dir;
    public:
    void draw_on_screen(){
        HANDLE hcon;
        hcon = GetStdHandle(STD_OUTPUT_HANDLE);

        SetConsoleCursorPosition(hcon,position.vector_to_coord());

        printf(sprite);
    }
    //aqui en el constructor me da error
    object(spr a_sprite,vector2 pos){
        sprite = a_sprite;
        position = pos;

    }

    void SetPos(vector2 pos){
        position = pos;
    }

    void SetDir(direction d_dir){
        dir = d_dir;
    }

    void SetSpr(spr a_sprite){
        sprite = a_sprite;

    }



};      

}

c++ dev-c++

asked by pmstd 30.05.2017 в 02:56

source

1 answer

Draw a picturebox, drawing lines and joining points How can I make a chronometer with seconds, milliseconds format? [closed]

score 1 · Answer 1

In C ++ the compiler is able to create a series of constructors ... as long as certain circumstances exist. For example, for the compiler to create the default constructor, it is necessary that:

No own constructor has been implemented
The default constructor has not been explicitly implemented

The first rule is not met in the case of vector2 :

struct vector2{
    vector2(float x,float y){ // <<--- Constructor propio
        this->x = x;
        this->y = y;
        }
};

Since you have not declared the constructor by default and the compiler is not going to create that constructor then an error occurs here:

class object{

    vector2 position; // (1)

    object(spr a_sprite,vector2 pos){ // (2)
        sprite = a_sprite;
        position = pos; // (3)
    }

The comments refer to the following:

Class object has a member variable of type vector2

By virtue of the previous point, in the constructor of object you must call some constructor of vector2 , since no constructor has been invoked explicitly the compiler tries to call the constructor by default. As said constructor is not found, the error is caused.

This is nothing more than a post-construction assignment.

The solution is to invoke the constructors instead of making assignments:

object(spr a_sprite,vector2 pos)
  : sprite(a_sprite), position(pos) // Llamadas a constructores
{
}