Hello.
I have existed class (for example Stream in phobos), and i need add
new method to it. In the past (if i correctly remember), i was able
to do it by defining function, that accept instance of class as
first argument, and then use it function like instance.function()

Now (DMD 1.70) i can't compile this code:

//////////////////////////////
class A
{
  int method1() { return 1; }
}

int method2(A a)
{
  return 2;
}

void main()
{
   A a = new A;
   int i = a.method1();
   int k = a.method2();
}
//////////////////////////////

Compiler say
1.d(20): no property 'method2' for type '1.A'

Can anyone say, what i missed, or the better way to "extend" existed class without declare new class based on existed? Thanks.

"novice2" <sorry@noem.ail> wrote in message news:eh4u36$2bsc$1@digitaldaemon.com...
> Hello.
> I have existed class (for example Stream in phobos), and i need add
> new method to it. In the past (if i correctly remember), i was able
> to do it by defining function, that accept instance of class as
> first argument, and then use it function like instance.function()
>...
> Can anyone say, what i missed, or the better way to "extend" existed class without declare new class based on existed? Thanks.

I don't think that ability has ever existed.  Maybe you're confusing it with the ability to do so with arrays?

int method(int[] x)
{
 return x.length;
}

void main()
{
 int[] arr = new int[10];
 int i = method(arr);
 int k = arr.method(); // equivalent to above
}

novice2 wrote:
> Hello.
> I have existed class (for example Stream in phobos), and i need add
> new method to it. In the past (if i correctly remember), i was able
> to do it by defining function, that accept instance of class as
> first argument, and then use it function like instance.function()
> 
> Now (DMD 1.70) i can't compile this code:
> 
> //////////////////////////////
> class A
> {
>   int method1() { return 1; }
> }
> 
> int method2(A a)
> {
>   return 2;
> }
> 
> void main()
> {
>    A a = new A;
>    int i = a.method1();
>    int k = a.method2();
> }
> //////////////////////////////
> 
> Compiler say
> 1.d(20): no property 'method2' for type '1.A'
> 
> Can anyone say, what i missed, or the better way to "extend"
> existed class without declare new class based on existed?
> Thanks.

It is, and was, only possible for arrays. But I sure wish it was possible for all types (classes, but int/float/etc too!)

L.

Lionello Lunesu wrote:
> novice2 wrote:
> 
>> Hello.
>> I have existed class (for example Stream in phobos), and i need add
>> new method to it. In the past (if i correctly remember), i was able
>> to do it by defining function, that accept instance of class as
>> first argument, and then use it function like instance.function()
>>
>> Now (DMD 1.70) i can't compile this code:
>>
>> //////////////////////////////
>> class A
>> {
>>   int method1() { return 1; }
>> }
>>
>> int method2(A a)
>> {
>>   return 2;
>> }
>>
>> void main()
>> {
>>    A a = new A;
>>    int i = a.method1();
>>    int k = a.method2();
>> }
>> //////////////////////////////
>>
>> Compiler say
>> 1.d(20): no property 'method2' for type '1.A'
>>
>> Can anyone say, what i missed, or the better way to "extend"
>> existed class without declare new class based on existed?
>> Thanks.
> 
> 
> It is, and was, only possible for arrays. But I sure wish it was possible for all types (classes, but int/float/etc too!)
> 
> L.

Argh!  Why so many special case rules for arrays?!

--bb

Lionello Lunesu wrote:
> novice2 wrote:
>>
>> Compiler say
>> 1.d(20): no property 'method2' for type '1.A'
>>
>> Can anyone say, what i missed, or the better way to "extend"
>> existed class without declare new class based on existed?
>> Thanks.
> 
> 
> It is, and was, only possible for arrays. But I sure wish it was possible for all types (classes, but int/float/etc too!)

By the way, where is that fun feature for arrays documented?  I can't seem to find it anywhere in the D spec at http://www.digitalmars.com/d/.

--bb

>Jarrett Billingsley (kb3ctd2@yahoo.com) 2006/10/18 08:49
>I don't think that ability has ever existed.  Maybe you're confusing it with
>the ability to do so with arrays?

Ah.. Only for arrays :(
Thank you for information.

Sorry for dumb question, but are there any
other ways to "extend" existed classes?
Inheritance only?

Bill Baxter wrote:
> By the way, where is that fun feature for arrays documented?  

It's not! (that's the most fun part!)

"novice2" <sorry@noem.ail> wrote in message news:eh5hi3$2v32$1@digitaldaemon.com...
> Ah.. Only for arrays :(
> Thank you for information.
>
> Sorry for dumb question, but are there any
> other ways to "extend" existed classes?
> Inheritance only?

Yep.  Some people have proposed something found in C#, where you can add methods to classes from outside the class, like:

class C
{
    int method()
    {
        return 10;
    }
}

int C.method2()
{
    return 20;
}

C c = new C();
c.method();
c.method2();

But this is not possible in D.

Hasan Aljudy wrote:
> Bill Baxter wrote:
>> By the way, where is that fun feature for arrays documented?  
> 
> It's not! (that's the most fun part!)

Must be to encourage everyone to read and participate in the news groups.  :-)