"dynamic constructor" in c++

Question

i am new to classes in C++ and i need to create a class "Plot" which has a method that reads in data from a file and creates a 3d grid.

i understand that you can make "default" constructors with default values or you can create a special constructor with predefined values.

in my "private" section, i have:

int nx; // number of "x" values
int ny; // number of "y" values
int nz; // number of "z" values
double* grid; // one dimensional array which stores nx*ny*nz values
double tgrid(int ix, int iy, int iz); // function which searches grid and returns value

now, i want to create my "plot" object and then AFTER that, dynamically create the "grid" array. is it possible to do this? or will i need to declare the size of the array "grid" when i first create "plot"?

Answer 1

Use std::vector grid; as your member. Then you can use grid.resize(nx*ny*nz) to force the size you want or use grid.push_back(value); for each value you want to add to the array.