initialize member array with constructor - c++

Question

I have a class School like this. Space is an abstract class, don't mind about it.
class school:public space
{
private:
schoolyard y;
stairs s;
floor floors[3];
int capa;
public:
school(int x):floors[1](x),floors[2](x),floors[3](x){
cout<<"a school has been created"<<endl;}
void move(student x);
~school();
};
floor is another class which I want to initialize. This part floors[1](x),floors[2](x),floors[3](x) is probably wrong. Maybe someone know how I can initialize an array of objects in a class?

Answer 1

Should be:
school(int x) : floors{x, x, x}
{
std::cout << "a school has been created" << std::endl;
}

Answer 2

First off, arrays are 0-based, so the valid indexes are 0-2, not 1-3.
Second, you can't initialize individual array members in a constructor's member initialization list like you are attempting to.
If floor does not have a default constructor, you can change your floors[] array to hold floor* pointers instead, and then construct each floor object using new in the constructor's body, eg:
class school : public space
{
private:
...
floor* floors[3];
...
public:
school(int x){
for (int i = 0; i < 3; ++i){
floors[i] = new floor(x);
}
// other initialization as needed...
cout << "a school has been created" << endl;
}
~school(){
for (int i = 0; i < 3; ++i){
delete floors[i];
}
}
...
};
Be aware that with this approach, you need to follow the Rule of 3/5/0, which means also implementing a copy constructor and a copy assignment operator, and optionally a move constructor and a move assignment operation in C++11 and later:
...
#include <algorithm>
class school : public space
{
private:
...
floor* floors[3];
...
public:
school(int x){
for (int i = 0; i < 3; ++i){
floors[i] = new floor(x);
}
// other initializations as needed...
cout << "a school has been created" << endl;
}
school(const school &src){
for (int i = 0; i < 3; ++i){
floors[i] = new floor(*(src.floors[i]));
}
// other copies as needed...
cout << "a school has been copied" << endl;
}
school(school &&src){
for (int i = 0; i < 3; ++i){
floors[i] = src.floors[i];
src.floors[i] = nullptr;
}
// other moves as needed...
cout << "a school has been moved" << endl;
}
~school(){
for (int i = 0; i < 3; ++i){
delete floors[i];
}
}
school& operator=(const school &rhs){
if (this != &rhs){
school temp(rhs);
std::swap_ranges(floors, floors+3, temp.floors);
}
return *this;
}
school& operator=(school &&rhs){
school temp(std::move(rhs));
std::swap_ranges(floors, floors+3, temp.floors);
return *this;
}
...
};
However, a std::vector would make things much easier, letting the compiler handle all of these details for you, eg:
...
#include <vector>
class school : public space
{
private:
...
std::vector<floor> floors;
...
public:
school(int x): floors(3, floor(x)) {
cout << "a school has been created" << endl;
}
...
};