[ruby-talk:00631] Re: Next misbehavior (sorry :-)

On 11 Aug, GOTO Kentaro wrote:
> Hi,
> 
> In message "[ruby-talk:00626] Next misbehavior (sorry :-)"
>     on 99/08/11, [e-mail] <[e-mail]> writes:
> 
>>Only `Object' and `Struct' instances seems to call `initialize'.
> 
> Matz said that initialize is a "getleman's agreement". Because, in
> some cases, it is too late to call initialize after the construction
> of object. For example, an array must be allocate memory when
> construction. Many predefined classes have such property. (sorry, I
> know my explain is not enough but I can't do well). 

Oh! I understand you, IMHO ;-)

I had the same problem with my class `Point' that I have coded in C for
my tutorial. But I have found a workaround, that I think that it solve
my problem. Better I show it to you, before it comes into the tutorial,
and THEN, people tell me how stupid I was ;-)

I try to code a class `Point' and later derive a class `Point3D' from
it....

First the `Point#new' method:

    VALUE
    pt_point_s_new(argc, argv, klass)
        int argc;
        VALUE *argv, klass;
    {
        VALUE obj;
    
        obj = Data_Wrap_Struct(klass, mark_point, free, NULL);
    
        rb_obj_call_init(obj, argc, argv);
    
        return obj;
    }

Then it follows `Point#initialize'...
    
    VALUE
    pt_point_init(argc, argv, self)
        int argc;
        VALUE *argv, self;
    {
        VALUE aX, aY;
        pt_RPoint *point;
        int args;
    
        if (DATA_PTR(self) == NULL)
            DATA_PTR(self) = ALLOC(pt_RPoint);
    
        args = rb_scan_args(argc, argv, "02", &aX, &aY);
    
        switch (args) {
            case 1: aY = INT2NUM(0); /* fall thru */
            case 0: aX = INT2NUM(0);
        }
    
        if (!IS_A(aX, rb_cNumeric) || !IS_A(aY, rb_cNumeric))
            rb_raise(rb_eTypeError, "wrong argument type: must be Numeric");
    
        Data_Get_Struc(obj, pt_RPoint, point);

        point->x = aX;
        point->y = aY;
    
        return self;
    }
    
So, I thought, I would not need a `Point3D#new' method, because I delay
the memory allocation until the instance is initialized via
`Point#initialize'! The nice side effect is, that I can let
`Point3D#initialize' allocate the memory for the `Point3D' instance.
The datatype `RPoint3D' is, of course, very similar to `RPoint' at the
beginning. Enhancements come later in the struct. But have a look...
    
    VALUE
    pt3_point_init(argc, argv, self)
        int argc;
        VALUE *argv, self;
    {
        VALUE aZ;
        int args;
    
        if (DATA_PTR(self) == NULL)
            DATA_PTR(self) = ALLOC(pt3_RPoint3D);
    
        pt_point_init(MIN(argc, 2), argv, self);
        
        aZ = ((argc == 3) ? argv[2] : INT2NUM(0));
    
        if (!IS_A(aZ, rb_cNumeric))
            rb_raise(rb_eTypeError, "wrong argument type: must be Numeric");
    
        RPOINT3D(self)->z = aZ;
    
        return self;
    }

As you can see, I reuse the `Point#init' method via `pt_point_init'.
And the same is true for all `pt_point_XXX' methods. And it also works
well, if I would code `Point3D' using Ruby. But, of course, I have to
call the `Point#initialize' method via `super' within from the
`Point3D#initialize' method.

Any objections?

[Very especial good code deleted (but not forgotten ;-)...]

I like your example (2) more than (1). I will chose it! Tkank you!!!

[...]

> It was requiested by me and some persons. Because we can't imagine a
> `new' numeric.

You and some persons are right, IMHO ;-)

> 
> -- gotoken

\cle