Overriding operator>> for a Strings class - c++

Question

I just have a quick question. I need to override the operator >> for a custom String class and I can't quite figure out how to do it.
I know that this code works, because it was my original method of solving the problem:
istream& operator>>(istream &is, String &s) {
char data[ String::BUFF_INC ]; //BUFF_INC is predefined
is >> data;
delete &s;
s = data;
return s;
}
However, according to the spec (this is a homework assignment), I need to read in the characters 1 at a time to manually check for whitespace and ensure that the string isn't too big for data[]. So I changed my code to the following:
istream& operator>>(istream &is, String &s) {
char data[ String::BUFF_INC ];
int idx = 0;
data[ 0 ] = is.get();
while( (data[ idx ] != *String::WHITESPACE) && !is.ios::fail() ) {
++idx;
is.get();
data[ idx ] = s[ idx ];
}
return is;
}
When this new code is executed however it just gets stuck in a loop of user input. So how do I use is.get() to read in the data character by character but not wait for more user input? Or should I perhaps be using something other than .get()?

Answer 1

You don't seem to be doing anything with the character you get from the stream
istream& operator>>(istream &is, String &s) {
char data[ String::BUFF_INC ];
int idx = 0;
data[ 0 ] = is.get();
while( (data[ idx ] != *String::WHITESPACE) && !is.ios::fail() ) {
++idx;
is.get(); // you don't do anything with this
data[ idx ] = s[ idx ]; // you're copying the string into the buffer
}
return is;
}
So it checks whether the string s contains a whitespace, not whether you read a whitespace from the stream.

Answer 2

Try:
istream& operator>>(istream &is, String &s)
{
std::string buffer;
is >> buffer; // This reads 1 white space separated word.
s.data = buffer.c_str();
return is;
}
Commenting on your original code:
istream& operator>>(istream &is, String &s)
{
char data[ String::BUFF_INC ];
is >> data; // Will work. But prone to buffer overflow.
delete s; // This line is definately wrong.
// s is not a pointer so I don;t know what deleting it would do.
s = data; // Assume assignment operator is defined.
// for your class that accepts a C-String
return s;
}
Using the second version as a base:
istream& operator>>(istream &is, String &s)
{
std::vector<char> data;
char first;
// Must ignore all the white space before the word
for(first = is.get(); String::isWhiteSpace(first) && is; first = is.get())
{}
// If we fond a non space first character
if (is && !String::isWhiteSpace(first))
{
data.push_back(first);
}
// Now get values while white space is false
char next;
while( !String::isWhiteSpace(next = is.get()) && is)
{
// Note we test the condition of the stream in the loop
// This is because is.get() may fail (with eof() or bad()
// So we test it after each get.
//
// Normally you would use >> operator but that ignores spaces.
data.push_back(next);
}
// Now assign it to your String object
data.push_back('\0');
s.data = data;
return is;
}