CODEWITHSUNDEEP
c++
user3457835
user3457835

Reputation: 3

Dynamic Allocation with pointers c++

Transaction *trans = new Transaction[MAX_NUM];
int currentnum;


addtrans(string balance, double amt){

    trans[currentnum] = new Transaction(balance, amt);
    currentnum ++;
}

//constructor

Transaction(string type, double amt){

      Transtype = type;
       Transamt = amt;
 }

I have created a pointer to an array.

I'm trying to send balance and amt to the array, but I am getting the error 'no match for 'operator=' '

Upvotes: 0

Views: 60

Answers (2)

Shoe
Shoe

Reputation: 76240

Use an std::vector instead:

std::vector<Transaction> trans;
trans.reserve(MAX_NUM);

and addtrans can be basically be reduced to:

trans.emplace_back(balance, amt);

Upvotes: 0

Tony Delroy
Tony Delroy

Reputation: 106116

Transaction *trans = new Transaction[MAX_NUM];

This gives you a pointer to an array of Transaction objects.

trans[currentnum] = new Transaction(balance, amt);

This tries to assign to a Transaction object in your array, but the new Transaction(...) call returns a pointer to a Transaction, and pointers are not the data element type for the array, so this won't compile.

You could say:

trans[currentnum] = Transaction(balance, amt);

Or, you could do this:

Transaction** trans = new (Transaction*)[MAX_NUM];
trans[currentnum] = new Transaction(balance, amt);

But it's almost certainly better to use:

std::vector<Transaction> trans(MAX_NUM);

If you really must have MAX_NUM default-constructed elements, or better yet...

std::vector<Transaction> trans;

And just .push_back(Transaction(balance,amt)) as you go, so you basically don't have to worry about any MAX_NUM or indexing off the end of the container. If you have a C++11 compiler you can use .emplace_back(balance, amt) for better performance and direct in-container construction of the Transaction object..

Upvotes: 2

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