Excel import

Posted 2020-09-09 lingdanglfw(DAX)

Case Study: Reading cell content from excel template for COM variant type VT_R4 or VT_R8 is always little tricky.
Observation: Reading real value can be done in following ways

1) num2Str0(_variant.double(), 0);

2) num2str(_variant.double(), 0, numOfDec(_variant.double()), 1, 0);

            Here is the output which is generated where the first function value is always a round-off value compared with the second function which returns the exact content with correct scale and precision.

COMVariantType Functions output for Real values.

 

/* 
Build excel template as following 
     and specify the path @ excel
=======================================
Column     Integer     Real                
=======================================
Rows(1)    123         60.9756097560976
Rows(2)    234         5.69105691056911
=======================================
*/

static void SR_VariantType(Filename excel = @‘C:\Projects\Data.xlsx‘)
{
    int                 rows;
    int                 columns;

    COMVariant          variant;
    SysExcelCells       sysExcelCells;
    SysExcelWorkbook    sysExcelWorkbook;
    SysExcelWorkbooks   sysExcelWorkbooks;
    SysExcelWorksheet   sysExcelWorksheet;
    SysExcelWorksheets  sysExcelWorksheets;
    SysExcelApplication sysExcelApplication;

    str variant2Str(COMVariant _variant)
    {
        str valueStr;
        ;

        switch(_variant.variantType())
        {
            case COMVariantType::VT_EMPTY   :
                valueStr = ‘‘;
                break;

            case COMVariantType::VT_BSTR    :

                valueStr = _variant.bStr();
                break;

            case COMVariantType::VT_R4      :
            case COMVariantType::VT_R8      :

                if(_variant.double())
                {
                    valueStr = strFmt("@SYS311964", 
                                      num2Str0(_variant.double(), 0),
                                      num2str(_variant.double(),
                                      0,
                                      numOfDec(_variant.double()), 
                                      1, 
                                      0));
                }
                break;

            default                         :
                throw error(strfmt("@SYS26908", 
                                   _variant.variantType()));
        }

        return valueStr;
    }
    ;

    sysExcelApplication = SysExcelApplication::construct();
    sysExcelWorkbooks   = sysExcelApplication.workbooks();

    try
    {
        sysExcelWorkbooks.open(excel, 
                               false /*Update links*/, 
                               true /*Read only*/);
    }
    catch (Exception::Error)
    {
        throw error(strFmt("@SYS76826", excel));
    }

    sysExcelWorkbook   = sysExcelWorkbooks.item(1);
    sysExcelWorksheets = sysExcelWorkbook.worksheets();

    // Only considering Sheet 1
    sysExcelWorksheet  = sysExcelWorksheets.itemFromNum(1);
    sysExcelCells      = sysExcelWorksheet.cells();

    // Since in first row there will be field names.
    for ( rows = 2; rows <= 3; rows++)
    {
        for (columns = 1; columns <= 2; columns++)
        {
            variant = sysExcelCells.item(rows, columns).value();
            print variant2Str(variant);
            pause;
        }
    }

    // Close Excel
    sysExcelApplication.quit();

    variant             = null;
    sysExcelWorkbooks   = null;
    sysExcelWorkbook    = null;
    sysExcelWorksheet   = null;
    sysExcelCells       = null;
    sysExcelApplication = null;
}