char and String in c++

I'm a Java developer but I have to develop application in C++.

I just want to read some data from database and set it in this:

struct Line{
    char* pdf1;
    char* pdf2;
    char* ident;
    char* reportpath ;
};

and I have this method:

void DBConnect()
{
    char* pdf1;
    char* pdf2;
    SAConnection con;
    lines=0;
    page[lines] = new Line();

    SACommand cmd(&con,"select from pdf where rownum<3 ");
    try
    {
        // connect to database (Oracle in our example)
        con.Connect("DB", "user", "password", SA_Oracle_Client);
        // Select from our test table
  开发者_如何学运维      cmd.Execute();
        // fetch results row by row and print results
        page[lines]->pdf1="PDF_CM";
        page[lines]->pdf2="PDF_LATEST";
        lines++;

        char *c1=new char(CELLSIZE);
        char *c2=new char(CELLSIZE);
        while(cmd.FetchNext())
        {
            page[lines] = new Line();
            string s1=cmd.Field("org_doc").asString();
            string s2=cmd.Field("rev_doc").asString();
            size_t t1=s1.find("text1");
            size_t t2=s2.find("text1");
            s1.replace(t1,std::string("text1").length(),"text2");
                s2.replace(t2,std::string("text1").length(),"text2");
            c1=new char(s1.size()+1);
            c2=new char(s2.size()+1);
            std::copy(s1.begin(), s1.end(), c1);
            std::copy(s2.begin(), s2.end(), c2);
            c1[s1.size()]='\0';
            c2[s2.size()]='\0';


            page[lines]->pdf1 =c1; 
            page[lines]->pdf2 =c2;
            s1.erase();
            s2.erase();
            ++lines;

        }
        con.Commit();
        con.Disconnect();
    }
    catch(SAException &x)
    {
        try
        {
            con.Rollback();
        }
        catch(SAException &)
        {
        }
        printf("%s\n", (const char*)x.ErrText());
    }
}

I get an error in the second while loop int this line:

string s1=cmd.Field("org_doc").asString();

But I can't know what the error is because I'm working in plugin :(

---

Apart from everything else this isn’t proper C++. It’s some mix of C and C++ code.

If you just replace the char* members with proper std::strings you will eliminate a whole host of problems (e.g. your erroneous allocation of the char buffers).

That is, your first step should be to eliminate char* and new from your code entirely and use std::string and automatic storage instead.

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The sql strings look suspicious, shouldn't it be

select * from pdf where rownum<3

The actual sql command might return a table with zero columns which would result in an error, if you tried to access field org_doc (which wouldn't be present in that case).

---

Glancing at the docs for SACommand it seems the SAString and string are unrelated types. SACommand is a MFC style string, which requires you to access the underlying buffer to use it as a string type object.

If the SAChar type is defined as a regular char you could do something like

string s1 = cmd.Field("org_doc").AsString().GetBuffer(min_length);