Vector of structs initialization

Question

I want know how I can add values to my vector of structs using the push_back method

struct subject
{
  string name;
  int marks;
  int credits;
};

         


        

Answer 1

You may also which to use aggregate initialization from a braced initialization list for situations like these.

#include 
using namespace std;

struct subject {
    string name;
    int    marks;
    int    credits;
};

int main() {
    vector sub {
      {"english", 10, 0},
      {"math"   , 20, 5}
    };
}

Sometimes however, the members of a struct may not be so simple, so you must give the compiler a hand in deducing its types.

So extending on the above.

#include 
using namespace std;

struct assessment {
    int   points;
    int   total;
    float percentage;
};

struct subject {
    string name;
    int    marks;
    int    credits;
    vector assessments;
};

int main() {
    vector sub {
      {"english", 10, 0, {
                             assessment{1,3,0.33f},
                             assessment{2,3,0.66f},
                             assessment{3,3,1.00f}
                         }},
      {"math"   , 20, 5, {
                             assessment{2,4,0.50f}
                         }}
    };
}

Without the assessment in the braced initializer the compiler will fail when attempting to deduce the type.

The above has been compiled and tested with gcc in c++17. It should however work from c++11 and onward. In c++20 we may see the designator syntax, my hope is that it will allow for for the following

  {"english", 10, 0, .assessments{
                         {1,3,0.33f},
                         {2,3,0.66f},
                         {3,3,1.00f}
                     }},

source: http://en.cppreference.com/w/cpp/language/aggregate_initialization