Re: How to elegantly store (and load) a string to (from) a file in binary mode?
Thanks to both of you. I was afraid that this is the case.
So anyway, I have tried to create Mystring to augment the
ability to save/load strings.
I am not too familiar with using dynamic polymorphism (inheritance)
becaused I used only static polymorphism (templates).
Anyway, for my limited purpose, I did the following tests which
I thought will be straight forward - I thought that a derived class/struct
inherite ALL the capabilities of the base class plus whatever other
capabilities I add to it. So here is a test program:
#include <string>
using namespace std;
struct Z : public string{};
struct MS : public string {
int save() {/*statements;*/ return 0;}
int load() {/*statements;*/ return 0;}
};
struct X{
MS s;
X():s(""){}; //first failure
}; //.\Test_2.cpp(10) : error C2664: 'MS::MS(const MS &)' : cannot convert parameter 1 from
'const char [1]' to 'const MS &'
// Reason: cannot convert from 'const char [1]' to 'const MS'
// No constructor could take the source type, or constructor overload resolution
was ambiguous
//*************************************
void main(int ac, char* av[])
{
Z sz; // OK
sz="z"; // failed: Z didn't inherite the operator '=', and so on
MS s1; // OK
s1="a"; // failed
MS sm("L"); // failed
sm="K"; // failed
X s2; // OK
s2.s="b"; // failed
X sa("L"); // failed
sm="L"; // failed
}
Obviously I miss something very fundamental. Especially in the simplest possible
case of type Z, where I would think is a synonym to the type 'string'.
What is it?
Thanks,
David
"Alex Blekhman" <xfkt@oohay.moc> wrote in message news:O3ASCwS6GHA.4176@TK2MSFTNGP02.phx.gbl...
"David F" wrote:
My goal is to save a struct X that contains as members
C++ strings (not String) to a file in binary mode and
later
be able to load it back to memory in binary mode.
Are there any built in methods to accomplish it in a
clean way? (If the strings would be C strings, there is no
problem).
If not, is there such a solution for an individual string?
No, there is no clean way. You will need to write/read each
member individually. Probbaly, also you will need to specify
each member's size during writing, so you will be able to
read it correctly. In case you're using std streams for file
I/O, then you need to provide `opertaor <<' and `operator
>>' for struct X. Inside these operators you do all dirty
work. If you use any other method for I/O, then call
`std::string::length' and `std::string::c_str'.
HTH
Alex