How to insert a value of a Qlist inside of another Qlist

[ofbrc]

I am trying to set a value inside a qlist of another qlist.

the code below gives me an error of ASSERT failure in QList<T> :: operator[] : "index out of range" .

main.hh

struct Order{
QList<OrderItem> items ;
}
 
struct OrderItem{
QString Address;
}
 
 
main.cpp
 
Ordergroup *ordergroup ;
 QList<Order> orderlist;
 for (int i = 0; i <3  ; ++i) {
      for (int j =0 ; j  < 3 ; ++j){
            if ( i == j){
                auto& refgr = orderlist[i];
                refgr.items[j].set(OrderItem::Address, "21 Street") ;
            }
       }
 }

struct Order{
QList<OrderItem> items ;
}

struct OrderItem{
QString Address;
}


main.cpp

Ordergroup *ordergroup ;
 QList<Order> orderlist;
 for (int i = 0; i <3  ; ++i) {
      for (int j =0 ; j  < 3 ; ++j){
            if ( i == j){
                auto& refgr = orderlist[i];
                refgr.items[j].set(OrderItem::Address, "21 Street") ;
            }
       }
 }

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I also tried the append but still it gives me an error of out of range.
If i set the the orderlist[i] into 1. it works but i need a set of arrays.
thanks in advance.