Unable to Access Struct Members within Template - c++

Question

I decided to make my HashTable class a template so I could practice making templates, but I've run into a problem. Within my HashTable<T> template, I have a data member array, called items of Buckets, which is a struct within the HashTable<T> class. After initializing items, I am unable to access the members of Bucket elsewhere in the template's code.
I have tried putting typename and template<class T> before the struct and variable definitions, but was unable to make it work.
Here is a snippet of code that gives me the error 'keyValue': undeclared identifier
#ifndef HASH_TABLE_
#define HASH_TABLE_
using namespace std;
#include <iostream>
template<class T>
class HashTable
{
public:
HashTable(int numItems) {
if (numItems <= 0) {
throw std::invalid_argument("Invalid HashTable size");
}
currItems = 0;
//B must be the next prime after 2 * numItems
B = 1000;
items = Bucket[B]; //allocate array of Buckets
items[0].keyVal; //ERROR: undeclared identifier
}
bool insert(T* newItem, int key) {
bool retVal = false;
if (currItems < B && newItem != NULL) { //cannot insert to full HashTable
int index = 0;
items[index].dataPtr = newItem; //ERROR:undeclared
items[index].keyVal = key; //ERROR:undeclared
retVal = true;
currItems++;
}
return retVal;
}
private:
struct Bucket {
T* dataPtr = NULL;
int keyVal = -1;
};
Bucket * items; //array of buckets
int B; //size of itemArray
int currItems; //track number of items in HashTable
};
#endif
Why does items[x] not access a Bucket, such that items[x].keyVal or items[x].dataPtr cannot be used? I've tried different types of initializations, such as items = new Bucket[B], but that hasn't worked either, so I am assuming my errors lie in the template side of things.
I appreciate any guidance!

Answer 1

You have to declare Bucket before you use it.
template<class T>
class HashTable
{
struct Bucket {
T* dataPtr = NULL;
int keyVal = -1;
};
public:
HashTable(int numItems) {
if (numItems <= 0) {
throw std::invalid_argument("Invalid HashTable size");
}
currItems = 0;
//B must be the next prime after 2 * numItems
B = nextPrime(numItems * 2);
items = new Bucket[B]; // <-- you forgot the 'new'
items[0].keyVal; //ERROR: undeclared identifier
}
bool insert(T* newItem, int key) {
bool retVal = false;
if (currItems < B && newItem != NULL) { //cannot insert to full HashTable
int index = getOpenBucket(key);
items[index].dataPtr = newItem; //ERROR:undeclared
items[index].keyVal = key; //ERROR:undeclared
retVal = true;
currItems++;
}
return retVal;
}
private:
Bucket * items; //array of buckets
int B; //size of itemArray
int currItems; //track number of items in HashTable
};
ps. do not do this: using namespace std; in header files - ever.
It is evil and antisocial as it poisons the global namespace of every cpp file that includes your header. It's a guaranteed way to ensure that no-one will ever use your library.