Re: [Vala] correct char ** binding

[Abderrahim Kitouni <a kitouni gmail com>]

Hello,

                      في ث، 08-03-2011 عند 17:57 +0100 ، كتب Jan Spurny:
> Hi Frederik,
>
> 'out string' will not work - that was the first thing I tried - problem is that if I would have used 'out 
> string' in 'setup' function, the generated C code will pass some temporary variable to 'setup' and not the 
> location of the required location. That is the reason why I've included that long explanation how it works. 
> Maybe I was not clear enough, so let me explain again:
>
> 1) 'setup' functions takes 'location' of 'char*' destionation variable and stores it along with 'name' in 
> 'SomeParser' structure
> 2) 'run' then does the parsing and fills all locations described by their names by previous 'setup' calls
> 3) now all destionations registered with 'setup' are filled

I see two solutions here: either you use ref (even if it wasn't really
supposed to be used like this, it assumes the reference is valid), or
you use pointers. I feel pointers are the right thing to do here, but
you should take care with memory management. I'd use:

public void setup(string name, string** location);

and then you use it:

string a = null;
x.setup("variable_a", &a);

Using ref would probably work as well, but I prefer pointers as that
will make it clear to the user of the API that there is something
unusual here.


> Another thing - I know that 'char *' is 'string', but why 'string a_str = a;' does not work?
You shouldn't know that ;-) Although they map to the same thing in C,
they are different things in Vala.

HTH,
Abderrahim