no matching function call to error in vector.push

I am getting the following error while compiling my C program:

error: no matching function for call to 'std::vector<ChainingTable<int>::Record, std::allocator<ChainingTable<int>::Record> >::push_back(ChainingTable<int>::Record*)'
  324 |         vector_.push_back(new Record(key, value));

The error is coming from the line:

template <class TYPE>
bool ChainingTable<TYPE>::update(const std::string &key, const TYPE &value)
{
    if (!keyExists)
        {
            vector_.push_back(new Record(key, value));
        }
}

This is defined for the class:

class ChainingTable : public Table<TYPE>
{
    struct Record
    {
        TYPE data_;
        std::string key_;
        Record(const std::string &key, const TYPE &data)
        {
            key_ = key;
            data_ = data;
        }
    };

    std::vector<std::vector<Record>> records_;
    int capacity_; // capacity of the array

Complete code:

int sz = numRecords();
bool rc = true;
std::hash<std::string> hashFunction;
size_t hash = hashFunction(key);
size_t idx = hash % capacity_;
std::vector<Record> vector_ = records_[idx];
bool keyExists = false;
for (int i = 0; i < vector_.size(); i  )
{
    if (vector_[i].key_ == key)
    {
        vector_[i].data_ = value;
        keyExists = true;
    }
}
if (!keyExists)
{
    vector_.push_back(new Record(key, value));
}

What could be the reason for this?

CodePudding user response：

Your vector is declared to store objects of type Record, not pointers to them (Record *) but you are trying to push result of operator new which returns Record *, just use std::vector::emplace_back instead:

vector_.emplace_back(key, value);

Note: in this line

std::vector<Record> vector_ = records_[idx];

you create a copy and later modify it, seems that you need a reference.

Note2: in your search loop you do not terminate even if you find object already, you should add break into if statement, that will make it more effective.

CodePudding user response：

The problem is that your variable vector_ holds objects of type Record but when you write:

vector_.push_back(new Record(key, value));

You are trying to add a pointer to a Record object in the vector vector_ instead of adding the Record object itself.

You can solve it by writing:

vector_.emplace_back(key, value);

Alternate solution

Note that there is another possible solution which is to use:

vector_.push_back(Record(key, value));

But using emplace_back should be preferred.