I need to instansiate an object and add it to an array. This is what I currently have in a method:
Row r;
rows[count] = r;
The problem here is r is on the stack and being removed after the function exits. I quick fix is to make r static but that is bad right? What should I do? (Sorry, complete C++ noob).
Edit: Removing the deconstructor for Row fixes the problem.
The line rows[count] = r copies the object r to the element at index count in the array. After that, it doesn't matter what happens to r, the array is unaffected.
[Edit: OK, it matters indirectly what happens to r - since the copy is using something that r can delete.]
This is surprising if you're used to (for example) Java, where an array element isn't actually an object, it's just a reference to one.
Row free anything in its destructor, and if so, does it have an operator= which copies whatever that is?
Row class is broken - when you copy an object you copy its pointer, but that doesn't stop the original deleting the thing that pointer points to. The difficult fix is to implement operator= and a copy constructor. The easy fix is to use a vector instead of an allocated array, so that there's nothing you need to do in the destructor of Row.
Use std::vector instead of the array, provided construction of Row is not arduous:
std::vector<Row> rows;
Row r;
rows.push_back(r);
When the vector goes out of scope, the destructor ~Row() will be called for each entry.
You can access the most recent added entry using either
const Row& last = rows.back();
or
size_t count = rows.size();
const Row& last = rows[count - 1];
In this case, you're actually creating it on the stack, and then copying the object to the location rows[count]. Note that if you created rows as an array of Row objects, there already was a Row object at that location, created with the default constructor, that you copied over.
For various reasons, in C++ we try to use the standard library containers like std::vector and std::list. These will expand to handle the new elements you add.
