C++ istream / ostream equivalent ?

[Pelle Månsson]

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.