Call to implicitly-deleted default constructor

Question

I get the error message Call to implicitly-deleted default constructor of 'std::array' when I try to compile my C++ project.

Header file cubic_patch.hpp

#include <array>
class Point3D{
public:
    Point3D(float, float, float);
private:
    float x,y,z;
};

class CubicPatch{
public:
    CubicPatch(std::array<Point3D, 16>);
    std::array<CubicPatch*, 2> LeftRightSplit(float, float);
    std::array<Point3D, 16> cp;
    CubicPatch *up, *right, *down, *left;
};

Source file cubic_patch.cpp

#include "cubic_patch.hpp"
Point3D::Point3D(float x, float y, float z){
    x = x;
    y = y;
    z = z;
}

CubicPatch::CubicPatch(std::array<Point3D, 16> CP){// **Call to implicitly-deleted default constructor of 'std::arraw<Point3D, 16>'**
    cp = CP;
}

std::array<CubicPatch*, 2> CubicPatch::LeftRightSplit(float tLeft, float tRight){
    std::array<CubicPatch*, 2> newpatch;
    /* No code for now. */
    return newpatch;
}

Could someone tell me what is the problem here, please ? I found similar topics but not really the same and I didn't understand the explanations given.

Thanks.

Answer 1

Two things. Class members are initialized before the body of the constructor, and a default constructor is a constructor with no arguments.

Because you didn't tell the compiler how to initialize cp, it tries to call the default constructor for std::array<Point3D, 16>, and there is none, because there is no default constructor for Point3D.

CubicPatch::CubicPatch(std::array<Point3D, 16> CP)
    // cp is attempted to be initialized here!
{
    cp = CP;
}

You can get around this by simply providing an initializer list with your Constructor definition.

CubicPatch::CubicPatch(std::array<Point3D, 16> CP)
    : cp(CP)
{}

Also, you might want to have a look at this code.

Point3D::Point3D(float x, float y, float z){
    x = x;
    y = y;
    z = z;
}

x = x, y = y, z = z doesn't make sense. You're assigning a variable to itself. this->x = x is one option to fix that, but a more c++ style option is to use initializer lists as with cp. They allow you to use the same name for a parameter and a member without the use of this->x = x

Point3D::Point3D(float x, float y, float z)
    : x(x)
    , y(y)
    , z(z)
{}