Creating array of structs in C++

arrays, c++, struct

Solution

Here is a bit modified version that creates edges in the function, and returns a vector containing all created edges.

#include <iostream>
#include <vector>

struct Edge {
    int position[4];
    int average;
};

std::vector< Edge > createEdges(int some_parameters){
    std::vector< Edge > edges( 8 );

    for(int i = 0 ; i < 8; i++){
        const Edge edge{ { 1, 0, 0, 0 }, 10 };

        edges[i] = edge;
    }

    return edges;
}


int main()
{
    auto e( createEdges(5));

    std::cout<<e[0].average<<std::endl;
}

There are few modifications :

- Instead of allocating an array of edges, and returning pointer, I return vector

- the way edge objects are created, and initialized (I think this is what is asked)

Problem

I'm having a newbie problem in C++. I have a struct `Edge` defined as following: ``` struct Edge { int position[4]; int average; }; ``` Now I need to create a lot of these structs and I created a helper-method for that, that creates an array of these structs based on some parameters: ``` Edge* createEdges(int some_parameters){ Edge *edges = new Edge[8]; for(int i = 0 ; i < 8; i++){ Edge edge; edge.position[0] = 1; //fill the rest of the edge array in the same manner edge.average = 10; edges[i] = edge; } return edges; } ``` However when I now call: `Edge *edges = createEdges(int some_parameters)` there is no sensible data in the Edge array (out of scope?). I think I'm mixing up some things here but I would prefer if I can make this work without resorting to the `vector` datastructures. Is this the normal way of handling this or should I declare the edge array myself and pass it to the helper method to fill it up? Edit: First of all, I want to thank everyone for there comments/hints/tips/advice/... they have helped me to find the problem that I overlooked so easily. After I seen the replies that the code should work, I tested the simplified code aswell (something I should have done in the 1st place) and surprisingly, it worked! So then I checked to see why my real code didn't work and the simplified version did. My real code looked like this: ``` Edge* createEdges(int some_parameters){ Edge* edges = new Edge[8]; if(some_parameter != 0){ //create the edges as in my 1st snippet return NULL; //doh, should return edges here ! } else { return NULL; } } ``` The reason why I had not seen that I simply returned the wrong value (NULL) was because the debugger showed me some `0xf6f6f6` addressess with some negative values for `edge.position` (something I don't quite understand, it should've just show me `0x000000`, perhaps I was just imagining things). All in all, this was an important lesson in why to never code after 3am, nothing good will come of it!

Original source