Question

I have some basic C++ design/syntax questions and would appreciate your reply.

• I have N number of regions
• Each region needs to store information about an object “element”

i.e. I want to achieve something like this:

region[i].elements = list of all the elements for region i.

Question 1:
Does the following syntax (see code below) / design look correct. Am I missing anything here?

EDIT

The instances of struct elem are created by some other class and its memory deallocation is handles by that class only I just want to access that object and its members using reg[i].elements list (vector) … so, how should I add these element objects to the vector “elements” in class Region?

//Already have this stucture that I need to use

struct elemt {
  int* vertex; 
  int foo1;
  double foo2;
};


class Region{
   public:
      // I am not sure what should be the syntax here! 
      // is it correct?
      std::vector <elemt*> elements;      
}

// Following is the constructor of "class A"
A::A(){
    // --header file defines: Region *reg;
    // Let numOfRegions be a class variable. ( changes based on "Mac"'s suggestion)
    numOfRegions = 100;
    //allocate memory:
    reg = new Region[numOfRegions];
}

A::~A(){
  delete [] reg;
  reg = NULL;
}

A::doSomething(){

// here I want to append the elements to the vector
// Let i be region 10. 
// Let e1 be an element of "struct elemt" that needs to be added

  reg[i].elements.push_back(e1);

}

Question 2:
Is the syntax in doSomething() correct? Later I want to run an iterator over all the elements in reg[i] and want to access, e1->foo1, e1->foo2 and like that.

Question 3:
In do something method, how do I ensure that e1 is not already in the “elements”

UPDATE

Corrected some syntax errors, and hopefully fixed memory leak noticed by user ‘Mac. ‘

Answer 1

First of all get rid of the memory leak from the code.

A::A(int numOfRegions = 100){

    m_reg = new Region[numOfRegions]; // define Region *m_reg in the class 
}

A::~A(){
  delete [] m_reg;
  m_reg = NULL;
}

You are allocating memory in the constructor and storing return address in local variable and it ll get destroyed when its scope is over .

You should store the base address so that you can delete it .