Building integer into string class

[dev_15]

Hi, this is one of the questions from Bruce Ekels thinking in C++ book, chapter 12, question 14, i have only posted the first part of the question that i am stuck with.

How do you combine an integer into the string class in C++?

Write a class called Bird that contains a string member and a static int. In the default constructor, use the int to automatically generate an identifier that you build in the string, along with the name of the class (Bird #1, Bird #2, etc.).

Thanks

[Anonymous]

I think the idea is that the integer is a static member. In the constructor it is incremented and then writeen to the string; that's the easy part. This way every instance has a unique numeric identifier in its string.

Oh... and teh easy part:

For a class with members:

static int index ;
std::string id_string ;

in the constructor you write the string thus:

index++ ;
id_string << "Bird #" << index ;

The string::operator<< is overloaded for const char* and int (amongst others), so it is as simple as that.

Clifford

[dev_15]

The compiler i'm using VC++ is saying:

error C2676: binary '<<' : 'std::string' does not define this operator or a conversion to a type acceptable to the predefined operator

[Soma]

Clifford loses track of his train of thought from time to time.

Search for 'std::ostringstream' and the 'std::ostringstream::str' method.

Soma

[Anonymous]

Doh! I am an idiot. Sorry.

Seeing as this is a Bloodshed/Dev-C++ forum, it would have been worth mentioning that you were using VC++ just out of courtesy.

Take a look at the example here: http://www.cplusplus.com/reference/iostream/ostringstream/ostringstream.html

Clifford

[Soma]

Well, it's not as if you are absolutely wrong. It just needs some support code.

Soma

template
<
typename Type_t
>
std::string &
operator <<
(
std::string & lhs_p,
const Type_t & rhs_p
)
{
std::ostringstream support;
support << rhs_p;
lhs_p += support.str();
return(lhs_p);
}