Reading/Writing Vector of Structs to/from Tab Delimited File

[jwwicks]

Hello All,

This is a student assignment. So I don't want the complete answer just a hint or maybe a bumb on the head cause I'm doing it the wrong way. Assume I haven't done anything braindead like not include a header etc... I can post the whole code if you like/need it but I'm trying to spare the forum :)

Got a product structure...

struct product {
    string id;
    string description;
    int quantity;
    double wholesale;
    double retail;
    Date* date_added;
};
 

Got a vector of products and a file for the data...

vector<product> Inventory;
ifstream inFile; //Input data file
ofstream outFile; //Output report file
 

Saved all the products to a tab delimited file, one product to each line using for_each...

 
for_each(Inventory.begin(), Inventory.end(), save_product(&outFile));
 
class save_product:public std::unary_function<product, bool>
{
private:
    ostream* m_os;
public:
    save_product( ostream* os ){ m_os = os; }
    bool operator()( const product& element )
    {
        bool ret_val = false;
        // save element in tab delimited format
        *m_os << element.id.c_str() 
            << "\t" << element.description.c_str() 
            << "\t" << element.quantity 
            << "\t" << element.wholesale 
            << "\t" << element.retail 
            << "\t" << element.date_added->get(2) // write date in month/day/year format
            << "/" << element.date_added->get(1) 
            << "/" << element.date_added->get(3) 
            << "\r\n";
        if(m_os)
            ret_val = true;
        return ret_val;
    }
};
 

No problem so far. The file is as I want it. But getting the data back into the vector is causing me some problems. I've seen the use of the copy algorithm for copying from a fstream to a vector but I need to tell the iterator to use tabs to delimit the text.... I wrote a functor load_product but what algorithm could I use to read the file in with...

 
// Copy doesn't quite do what I want with data...
copy( istream::iterator<T>(inFile), istream::iterator<T>(), back_inserter(Inventory) );
 
class load_product:public std::unary_function<product, bool>
{
private:
    istream* m_is;
public:
    load_product( istream* is ){ m_is = is; }
    bool operator()( product& element )
    {
        bool ret_val = false;
        char buffer[maxStringSize];
        stringstream ioConv;
        unsigned int fieldCnt = 0;
 
        while(m_is && fieldCnt < REC_FIELD_COUNT )
        {
            m_is->getline(buffer,(streamsize)maxStringSize, '\t');
            if(m_is)
            {
                switch( fieldCnt )
                {
                    case 0: element.id = buffer; break;
                    case 1: element.description = buffer; break;
                    case 2: ioConv >> buffer; ioConv << element.quantity; break;
                    case 3: ioConv >> buffer; ioConv << element.retail; break;
                    case 4: ioConv >> buffer; ioConv << element.wholesale; break;
                    default:
                        element.date_added->set(buffer, "/");
                        break;
                }
            }
            fieldCnt++;
            if( fieldCnt == REC_FIELD_COUNT && m_is ) ret_val = true;
        }
 
        return ret_val;
    }
};
 
 

I can do this manually with a while sure but I was hoping for a more elegant/STL way of doing it...

Thanks for any guidance...
John

[jwwicks]

Hello All,

 
// Copy doesn't quite do what I want with data...
copy( istream::iterator<T>(inFile), istream::iterator<T>(), back_inserter(Inventory) );
 
class load_product:public std::unary_function<product, bool>
{
private:
istream* m_is;
public:
load_product( istream* is ){ m_is = is; }
bool operator()( product& element )
{
bool ret_val = false;
char buffer[maxStringSize];
stringstream ioConv;
unsigned int fieldCnt = 0;
 
while(m_is && fieldCnt < REC_FIELD_COUNT )
{
m_is->getline(buffer,(streamsize)maxStringSize, '\t');
if(m_is)
{
switch( fieldCnt )
{
case 0: element.id = buffer; break;
case 1: element.description = buffer; break;
case 2: ioConv >> buffer; ioConv << element.quantity; break;
case 3: ioConv >> buffer; ioConv << element.retail; break;
case 4: ioConv >> buffer; ioConv << element.wholesale; break;
default:
element.date_added->set(buffer, "/");
break;
}
}
fieldCnt++;
if( fieldCnt == REC_FIELD_COUNT && m_is ) ret_val = true;
}
 
return ret_val;
}
};
 
 

Thanks for any guidance...
John

I think I may have found the answer on another thread...
http://www.thescripts.com/forum/thread436124.html

It involves the post about a Proxy for the istream_iterator...

John