overload operator problem

hanna88

hey there.
i'm having trouble to change my initial code to the one that uses stl vector.
i construct a new constructor vector<int>array to replace int*array.

but what about other steps? are there any major changes with the method if i'm trying to use stl vector?

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class My_Array 

{
 
    int * array;

    int count;
 
public:
 
    My_Array & operator = (const My_Array & other)

    {

        if (this != &other) 

        {
 
            int * new_array = new int[other.count];

            std::copy(other.array, other.array + other.count, new_array);
 
            delete [] array;
 
            array = new_array;

            count = other.count;

        }
 
        return *this;

    }
 
};

i appreciate any help

Banfa

Your question isn't clear you talk about having changed from using int * accessed dynamic arrays to vector<int> but then you post code that hasn't had this done to it.

weaknessforcats

First, your My_Array::operator= doesn't work.

Since you return a reference, what you return must be exactly the original object but you have made a copy of the array so you don't have a reference.

You need to return *this.

But that means you need to make a My_Array object so you can return a referecne to that. Unfortunately, that will be a local object and you can't return a reference to a local object.

In short, your assignment operator needs to return a My_Array object and not a reference to one.

As to using vector<int>, C++ requires that vector<> implement a real array. Just like you are doing. This means that all of the vector<> member functions are direct replcements for the code you will write for My_Array. Plus yure code is non-standard and only works for the int type unless you make a template, which vector<> is already.

Therefore,

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vector<int> obj;

completely replaces all of your code with standard code that everyone knows about.

So, unless this is some homework assignment, you should vector<> and never use native arrays or classes that you write that use native arrays.

hanna88

this is what i got so far

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 class My_Array  

{ 
 
    vector<int>array; 

    int count; 
 
public: 
 
    My_Array & operator = (const My_Array & other) 

    { 

        if (this != &other)  

        { 
 
            vector<int> new_array = new vector<int>; 

            std::copy(other.begin(), other.end(), new_array); 
 
            //is there other way to delete vector<int>array without creating a nre pointer for it?

            delete array; 

  //does vector has it's own assigment because this part here didnt work.

            array = new_array; 

            count = other.count; 

        } 
 
        return *this; 

    } 
 
};

Banfa

int count is no longer required once you start using vector. vector has a member function that can return it's size.

Your if statement isoverly complex it can simplify to this

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       if (this != &other)  

        { 

            array = other.array;

        }

hanna88

if i do it that way can the operators be chained? like (A=B=C) ?

Banfa

chaining is about the return value and parameters of the operator. It has nothing to do with how it is implemented, or rather it if the implementation is correct for A = B and you have the correct return value then it'll work in a chain too.

hanna88

thanks heaps for your help.now i get it. :)

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