On 12/02/2010 09:05 AM, vincent picaud wrote:
Matthias Pleh Wrote:
Thank you for your reply and yes that works :)
Now i m facing with the following problem, what is the trick for input stream ?
( something like
std::istream& operator>>(std::istream& in,A& a)
{
// A.someData<< in;
return in;
}
in C++ )
I m thinking of the situation when we want to load some data from a file.
The toString() trick is okay for saving the object... but how to load it back
(something like fromString(char[]) would do the job but it does not exist in
Object) ?
Anyway thank you, you solved half of my problem :)
Ther are many posibilities, depending on your further needs! Just have a
look at the online dokumentation:
http://www.digitalmars.com/d/2.0/phobos/phobos.html
But my first try would be such ..
(note: I've leaved out error-handling ...)
module test;
import std.stdio;
import std.file;
class A
{
void writeToFile() { std.file.write("sample.txt",someData); }
void readFromFile() { someData=cast(string)read("sample.txt"); }
void clear() { someData="n/A\n"; }
string toString() { return someData; }
private:
string someData="Just some data.
With anohter line of date.
Even more data.!";
}
int main(string[] args)
{
A a=new A;
a.writeToFile();
a.clear();
writeln(a);
a.readFromFile();
writeln(a);
return 0;
}
thank you for all your answers. I understand the approach, but in the same
time, I have the feeling that the C++ way is more convenient.
Look in C++ , to define I/O for A, you do not have to modify your class A and
simply have to overload two functions:
std::ostream& operator<<(std::ostream& out,const A& a)
std::istream& operator>>(std::istream& in,A& a)
moreover this smoothly extend the I/O C++ framework without other side effect.
I was expecting to find a similar mecanism in D/Phobos
Perhaps by overloading some read(), write() functions of the Phobos library, but I do not
know if it is "moral" to do that and which phobos functions are concerned...
IMHO there is a documentation hole here
What you want is the new writeTo system for output. For input, a
readFrom would be symmetrical and make sense :-)
To actually use it, you would just do myFile.write(your, stuff, etc);
For now, you can stringify using toString(). No way to read yet, except
to!int, etc.
