Thread: I still need help on this!

How do I initialize my templated array class??

So let's say my template class is this...

template <class T>
class RArray {
private:
typedef enum { StartArraySize = 128} bogus;
typedef enum {InitialSize = 0};

size_t num_elem;

size_t array_size;

size_t array_Cursor;

T *pArray;


private:

public:


I can add an init routine like this?


RArray()
{
pArray = new T[ StartArraySize ];
num_elem = InitialSize;
array_Cursor = InitialSize;
array_size = StartArraySize;
}


Like this?

void Init()
{
int i = 0;
for (;i< StartArraySize;i++)
{
pArray[i] = 0;
}
pArray
}


~RArray()
{
if (pArray != NULL) {
delete [] pArray;
}
}

pretend i have this..(example)

Code:

template<class t>
class test
{
public:
test();
int somefunction();
};

// to define it outside the class you need to do this
template<class t>
test<t>::test()
{
//default constructor..whatever you want!
}

template<class t>
int test<t>::somefunction()
{
//still whatever you want
}

hope that helps

also did you know you can do this?

Code:

template<class t, int num> //<---look at that
class test
.
.
.
.
//in the constructor
template<class t, int num>
test<t, num>::test()
{
pArray = new t[num]; // the person can make array any size they want
...
..
}

int main()
{
test<int, 20> array; //wow array of 20

return 0; // very famous
}

also your class definition is just like a "blue print" so you can not initialize anything in the class, but you can assign it stuff in the constructor etc..or other functions...instead of using

Code:

void Init()

put the body of that function in the constructor...much better

you sorta can..its in the constructors..look

you cant do this

Code:

class test
{
private:
int number = 5;
};

nope wrong!

but you can do this

Code:

class test
{
private:
int number;
public:
test(int x = 5): number(x) {}
};

// or
class test
{
private:
int number;
public:
test(int x = 5)
{
number = x;
}
};

now you get it?

I guess what confuses me is that since my template is generic and is supposed to take any "type" that I pass it, how would I set all of its initial elements to NULL or zero or whatever? Is this even a good idea for a template since I will be overwriting the entries eventually anyway?

the almighty beautiful "for" loop and set it equal to 0;
and i think NULL is another keyword for 0 (really means same i think...i read it somewhere in my book or so)

so

Code:

int* pnum = NULL;
int* pnum2 = 0; //both points to nothing

hehe..hope that helps

RArray()
{
int i = 0;
num_elem = num;
array_Cursor = sizeof(0);
pArray = new T[num];

for(;i<num;i++)
{
pArray[i] = array_Cursor;
//also with 0 or NULL
}

}
My compiler says the equal operator is ambiguous...


--------------------Configuration: ADOXperiment - Win32 Debug--------------------
Compiling...
ADOXperiment.cpp
d:\data\vss\coderesearch\adoxperiment\debug\msadox .tlh(1201) : warning C4146: unary minus operator applied to unsigned type, result still unsigned
d:\data\vss\coderesearch\adoxperiment\debug\msado1 5.tlh(409) : warning C4146: unary minus operator applied to unsigned type, result still unsigned
d:\data\vss\coderesearch\adoxperiment\rarray.h(85) : error C2593: 'operator =' is ambiguous
d:\data\vss\coderesearch\adoxperiment\rarray.h(75) : while compiling class-template member function '__thiscall RArray<class _variant_t,100>::RArray<class _variant_t,100>(void)'
Error executing cl.exe.

ADOXperiment.exe - 1 error(s), 2 warning(s)

what is num equal to? your didnt put anything in your constructor to take values

RArray()

.....think of the constructor as a regular function
also..pArray[i] = 0; // good enough dont use sizeof(0)

I don't need to with this syntax my code is smaller

template <class T, int num>
class RArray {
....

I called it this way

// Create instance of the templated array class. Establish that
// it will be holding _variant_t data types.

RArray< _variant_t,100 > BookMarks;

Compiler says ok and it runs....

RArray()
{
int i = 0;
num_elem = num;
array_Cursor = sizeof(0);
pArray = new T[num];

for(;i<num;i++)
{
pArray[i] = 0;
}

}

I passed it a "num" when I declared it in the function where it's used..

int ArchiveTable(const char* copiedTableName,const char* alsoCopiedTable,const char* dataSource)
{
// Return negative one if table name and datsource are null.
if (!copiedTableName || !dataSource || alsoCopiedTable)
return -1;

// Declare and initialize local variables.
bool bSuccessful = false;
enum DataTypeEnum columnType = adDate;
long columnCount = 0;


// Define ADOX variable types.
HRESULT hr = S_OK;
_bstr_t columnName;
_variant_t vIndex;
_variant_t vNull;



// Create instance of the templated array class. Establish that
// it will be holding _variant_t data types.

.... RArray< _variant_t,100 > BookMarks;

other fun stuff