Using late binding in CPP

Prerequisites

Please register Aspose.PDF for .NET with COM Interop, kindly check the article named Use Aspose.pdf for .NET via COM Interop.

Sample

This is a simple C++ code sample to extract text from PDF by means of COM Interop using late binding. For details please look at this post.

#include "pch.h"
#include "comdef.h"

using namespace System;

String^ lateBinding(String^ file)
{
    String^ text;
    DISPID dispid;
    DISPPARAMS dp = { NULL, NULL, 0, 0 };
    VARIANTARG vargs[1];
    VARIANT arg, result;
    WCHAR str[255];
    CLSID pclsid;

    // Create ComHelper
    IDispatch* comHelperPtr;

    wcscpy_s(str, L"Aspose.Pdf.ComHelper");
    CLSIDFromProgID(str, &pclsid);

    HRESULT hr = CoCreateInstance(pclsid, NULL, CLSCTX_ALL, IID_IDispatch, (void**)&comHelperPtr);
    if (FAILED(hr))
    {
        Console::WriteLine(L"Error occured");
    }
    else
    {
        // Set license
        IDispatch* licPtr;
        wcscpy_s(str, L"Aspose.Pdf.License");
        CLSIDFromProgID(str, &pclsid);

        HRESULT hr = CoCreateInstance(pclsid, NULL, CLSCTX_ALL, IID_IDispatch, (void**)&licPtr);

        OLECHAR* setLicense = L"SetLicense";

        hr = licPtr->GetIDsOfNames(IID_NULL, &setLicense, 1, GetUserDefaultLCID(), &dispid);
        arg.vt = VT_BSTR;

        BSTR lic = SysAllocString(L"C:\\Temp\\Aspose.Pdf.lic");

        arg.bstrVal = lic;

        vargs[0] = arg;

        dp.rgvarg = vargs;

        dp.cArgs = 1;

        hr = licPtr->Invoke(dispid, IID_NULL, GetUserDefaultLCID(), DISPATCH_METHOD, &dp, &result, NULL, NULL);

        SysFreeString(lic);

        licPtr->Release();

        // Get Document

        OLECHAR* openFile = L"OpenFile";

        hr = comHelperPtr->GetIDsOfNames(IID_NULL, &openFile, 1, GetUserDefaultLCID(), &dispid);

        arg.vt = VT_BSTR;

        arg.bstrVal = (BSTR)System::Runtime::InteropServices::Marshal::StringToBSTR(file).ToPointer();

        vargs[0] = arg;

        dp.rgvarg = vargs;

        dp.cArgs = 1;

        hr = comHelperPtr->Invoke(dispid, IID_NULL, GetUserDefaultLCID(), DISPATCH_METHOD, &dp, &result, NULL, NULL);

        IDispatch* docPtr = result.pdispVal;

        comHelperPtr->Release();

        // Get Pages for the Document

        OLECHAR* pages = L"Pages";

        hr = docPtr->GetIDsOfNames(IID_NULL, &pages, 1, GetUserDefaultLCID(), &dispid);

        dp.cArgs = 0;

        hr = docPtr->Invoke(dispid, IID_NULL, GetUserDefaultLCID(), DISPATCH_PROPERTYGET, &dp, &result, NULL, NULL);

        IDispatch* pagesPtr = result.pdispVal;

        // Create Absorber

        IDispatch* absorberPtr;

        wcscpy_s(str, L"Aspose.PDF.Text.TextAbsorber");

        CLSIDFromProgID(str, &pclsid);

        hr = CoCreateInstance(pclsid, NULL, CLSCTX_ALL, IID_IDispatch, (void**)&absorberPtr);

        // Browse text

        arg.vt = VT_DISPATCH;

        arg.pdispVal = absorberPtr;

        vargs[0] = arg;

        dp.rgvarg = vargs;

        dp.cArgs = 1;

        OLECHAR* accept_4 = L"Accept_4";

        hr = pagesPtr->GetIDsOfNames(IID_NULL, &accept_4, 1, GetUserDefaultLCID(), &dispid);

        hr = pagesPtr->Invoke(dispid, IID_NULL, GetUserDefaultLCID(), DISPATCH_METHOD, &dp, &result, NULL, NULL);

        // Retrieve text

        OLECHAR* _text = L"Text";

        dp.cArgs = 0;

        hr = absorberPtr->GetIDsOfNames(IID_NULL, &_text, 1, GetUserDefaultLCID(), &dispid);

        hr = absorberPtr->Invoke(dispid, IID_NULL, GetUserDefaultLCID(), DISPATCH_PROPERTYGET, &dp, &result, 0, 0);

        text = gcnew String(result.bstrVal);

        docPtr->Release();

        pagesPtr->Release();

        absorberPtr->Release();

    }

    return text;
}

int main(array<System::String^>^ args)
{
    if (args->Length != 1)
    {
        Console::WriteLine("Missing parameters\nUsage:testCOM.exe <pdf file>");
        return 0;
    }

    CoInitialize(NULL);
    String^ text = lateBinding(args[0]);
    CoUninitialize();
    Console::WriteLine("Extracted text:");
    Console::WriteLine("---\n{0}", text != nullptr ? text->Trim() : "<empty>");
    Console::WriteLine("---");
    return 0;
}