Re: return string

From:

"Jim Langston" <tazmaster@rocketmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 16 Apr 2008 19:59:33 -0700

Message-ID:

<r2zNj.110$aW3.39@newsfe06.lga>

Eric Kaplan wrote:

I have a function like this
=============
bool Table::Get(char* FieldName, char* FieldValue)

and I call the function like the follow
=============
while(!tbl.ISEOF())
{
char id2[300];
if(tbl.Get("program",id2))
cout<<"program:"<<id2<<endl;
else
{
tbl.GetErrorErrStr(ErrStr);
cout<<"\n"<<ErrStr<<"\n";
break;
}

}

above I passed in a char pointer (char*) - FieldValue and use it just
like a return value.

but it seem not efficient as each time i initialize a char array of
[300] characters.

but some string (FieldValue) is only like [5] char.

how to I do better for returning string? any example code?

Instead of using a c-style string, you would be better to use a std::string
which is dynamically sized. You can copy from/to c-style strings relatively
easy.

bool Table::Get( char* FieldName, std::string& FieldValue )
{
   // Determine the data that FieldValue is to get. You'll probably get a
pointer
   // to a c-style string somewhere returned from some database.
   // for an example:
   char data[] = "12345678";

  FieldValue = data;
}

The key to it is assigning std::string = char* will dynamically size the
string to hold the amount of characters needed.

Now to call it:

while(!tbl.ISEOF())
{
  std::string id2;
  if (tbl.Get("program", id2))
  cout<<"program:"<<id2<<endl;
  else
  {
     tbl.GetErrorErrStr(ErrStr);
     cout<<"\n"<<ErrStr<<"\n";
     break;
  }
}

=================

should I just return the string in regular return type like -
std::string Table::Get(char* FieldName)

You could, yes. You seem to know about std::string yet didn't realize you
could pass a reference to a std::string just as you can a char pointer.

--
Jim Langston
tazmaster@rocketmail.com