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From: Vijaya Kumar B.H. on 2 Apr 2008 09:46
I am working on a project where i have to do same processing for all the
members of the structure. The problem is the struct is very huge (with about
20 ints) and i have to write the specific function to each structure member.

I am a java programmer also , java has a concept called reflection which
helps to extract the members from the object. I am just wondering if such a
way is available in C++. I saw few external libraries which can do such
thing but they involve log of changes in structure.

any better idea ?

Vijay


From: Bart van Ingen Schenau on 2 Apr 2008 12:56
Vijaya Kumar B.H. wrote:

> I am working on a project where i have to do same processing for all
> the members of the structure. The problem is the struct is very huge
> (with about 20 ints) and i have to write the specific function to each
> structure member.
>
> I am a java programmer also , java has a concept called reflection
> which helps to extract the members from the object. I am just
> wondering if such a way is available in C++. I saw few external
> libraries which can do such thing but they involve log of changes in
> structure.
>
> any better idea ?

If it occurs frequently that you need to apply the same operation to all
(or a large portion) of the data members, you could choose to declare
them as a single array (provided they all have the same type). When you
need to access a particular member, you can use an enumeration to give
the members a name.

For example:

class Foo
{
private:
enum {
first_member,
boo,
bar,
num_members /* must be last! */
};
int data[num_members];
public:
void increment_all()
{
for (int i=0; i<num_members; i++)
data[i]++;
}
int get_boo()
{
return data[boo];
}
};

>
> Vijay

Bart v Ingen Schenau
--
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From: Francis Glassborow on 3 Apr 2008 07:25
Bart van Ingen Schenau wrote:
> Vijaya Kumar B.H. wrote:
>
>> I am working on a project where i have to do same processing for all
>> the members of the structure. The problem is the struct is very huge
>> (with about 20 ints) and i have to write the specific function to each
>> structure member.
>>
>> I am a java programmer also , java has a concept called reflection
>> which helps to extract the members from the object. I am just
>> wondering if such a way is available in C++. I saw few external
>> libraries which can do such thing but they involve log of changes in
>> structure.
>>
>> any better idea ?
>
> If it occurs frequently that you need to apply the same operation to all
> (or a large portion) of the data members, you could choose to declare
> them as a single array (provided they all have the same type). When you
> need to access a particular member, you can use an enumeration to give
> the members a name.
>
> For example:
>
> class Foo
> {
> private:
> enum {
> first_member,
> boo,
> bar,
> num_members /* must be last! */
> };
> int data[num_members];
> public:
> void increment_all()
> {
> for (int i=0; i<num_members; i++)
> data[i]++;
> }
> int get_boo()
> {
> return data[boo];
> }
> };
>
Or youy can create an array and then declare references to individual
elements to give them names:

class Foo {
public:
// whatever
private:
static int const datacount = 20;
int data[datacount];
int & first(data[0]);
int & second(data[1]);
// etc. but with more meaningful names
};

Now you can access the data as an array when you want to process all the
members the same way or by name when you want the individual elements.
From: Vijaya Kumar B.H. on 3 Apr 2008 09:02
Thanks Francis , Schenau I will try these methods

Vijay
"Francis Glassborow" <francis.glassborow(a)btinternet.com> wrote in message
news:r6qdnVPRSOc5I2nanZ2dnUVZ8v6dnZ2d(a)bt.com...
> Bart van Ingen Schenau wrote:
>> Vijaya Kumar B.H. wrote:
>>
>>> I am working on a project where i have to do same processing for all
>>> the members of the structure. The problem is the struct is very huge
>>> (with about 20 ints) and i have to write the specific function to each
>>> structure member.
>>>
>>> I am a java programmer also , java has a concept called reflection
>>> which helps to extract the members from the object. I am just
>>> wondering if such a way is available in C++. I saw few external
>>> libraries which can do such thing but they involve log of changes in
>>> structure.
>>>
>>> any better idea ?
>>
>> If it occurs frequently that you need to apply the same operation to all
>> (or a large portion) of the data members, you could choose to declare
>> them as a single array (provided they all have the same type). When you
>> need to access a particular member, you can use an enumeration to give
>> the members a name.
>>
>> For example:
>>
>> class Foo
>> {
>> private:
>> enum {
>> first_member,
>> boo,
>> bar,
>> num_members /* must be last! */
>> };
>> int data[num_members];
>> public:
>> void increment_all()
>> {
>> for (int i=0; i<num_members; i++)
>> data[i]++;
>> }
>> int get_boo()
>> {
>> return data[boo];
>> }
>> };
>>
> Or youy can create an array and then declare references to individual
> elements to give them names:
>
> class Foo {
> public:
> // whatever
> private:
> static int const datacount = 20;
> int data[datacount];
> int & first(data[0]);
> int & second(data[1]);
> // etc. but with more meaningful names
> };
>
> Now you can access the data as an array when you want to process all the
> members the same way or by name when you want the individual elements.


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