I have a class hi with a non-default constructor taking two arguments. I'm trying to construct an array of his:
class hi {
public:
hi(int a, int b){};
};
int main() {
hi *hello;
int number_of instance = 5;
hello = new hi[number_of_instance]; // (1)
}
How to invoke hi::hi(int,int) on the line marked (1)?
How to invoke
hi::hi(int,int)?
If hi is actually an aggregate type and/or you're using C++11, you can built it simply with:
hello = new hi[5]{{1, 2}, {3, 4}, {5, 6}, {7, 8}, {9, 10}};
If hi is not an aggregate, per se you cannot. But with a bit of improvement, we can achieve it.
This gives:
class hi {
hi();
public:
hi(int a, int b){};
};
Thhe idea is to provide a default constructor for the standard container to find, even though std::is_default_constructible_v<hi> is false. Obviously, any actually attempt to default construct an hi will end in a compilation failure.
std::array or a std::vector instead of a C array:This gives:
std::vector<hi> his;
std::generate_n to construct your objects:This gives:
his.reserve(number_of_instances);
std::generate_n(std::back_inserter(his), number_of_instances, [](){ return hi{0, 0}; });
Note though, this vector as a vector of non-default constructibe type is uncomplete, you'll be unable to use all of its features.
Another approach would be to reserve some memory as arrays of unsigned char and construct his instances in it with placement news.
begin(his) == end(his)
std::generate_n(std::back_inserter(his), number_of_instances, [](){ return hi{0, 0}; });
Use a vector
std::vector<hi> hello{{1,2},{1,2},{1,2},{1,2},{1,2}};
hello = new hi[5]{{1, 2}, {3, 4}, {5, 6}, {7, 8}, {9, 10}};