• macky (30/30) Apr 12 2007 Hi all!
• Jarrett Billingsley (5/41) Apr 12 2007 What _are_ you doing, anyway? Why do you need to use .tupleof to do
• macky (3/54) Apr 13 2007 ah. sorry. Classes are empty due to my lazyness ;). Actualy there are so...
• Jarrett Billingsley (31/43) Apr 13 2007 Ah, I see now. Depending on what you're trying to do, tupleof might be
• macky (3/56) Apr 15 2007 You're right! Serialization is just one of the benefit comming from this...
• macky (3/64) Apr 16 2007 I found a solution, though I'm not sure why things behave like this...

macky <martin.butina gmail.com> writes:

Hi all!

I'm trying to figure out how dynamic polymorhism is done the right way in D...

interface I
{
    ...some required functions...
}

class BaseClass()
{
    ...implementation of interface...
}

class Customer() : BaseClass
{
   ...some members and overriden baseclass functions...
}

class Process()
{
    void DoSomething(BaseClass object)
    {
        //I want to process all classes derived from base class
    }
}

void Main()
{
   Customer customer = new Customer();
   Process process = new Process();
   process.DoSomething(customer);
}

Even though this is working tupleof is not returning any value (I suppose
becouse when creating an instance customer is casted in base class and the link
is broken - actualy we are dealing with a partial clone).
Is this the right way of doing things? I know that in c++ you should provide a

provided by reference. I tried to provide a "ref" in the input params ( void
DoSomething(ref BaseClass object)) but this is not accepted. How can I solve
this? Thanx.

br, Martin

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"macky" <martin.butina gmail.com> wrote in message 
news:evksq3$223e$1 digitalmars.com...
 Hi all!

 I'm trying to figure out how dynamic polymorhism is done the right way in 
 D...

 interface I
 {
    ...some required functions...
 }

 class BaseClass()
 {
    ...implementation of interface...
 }

 class Customer() : BaseClass
 {
   ...some members and overriden baseclass functions...
 }

 class Process()
 {
    void DoSomething(BaseClass object)
    {
        //I want to process all classes derived from base class
    }
 }

 void Main()
 {
   Customer customer = new Customer();
   Process process = new Process();
   process.DoSomething(customer);
 }

 Even though this is working tupleof is not returning any value (I suppose 
 becouse when creating an instance customer is casted in base class and the 
 link is broken - actualy we are dealing with a partial clone).
 Is this the right way of doing things? I know that in c++ you should 

 everything is provided by reference. I tried to provide a "ref" in the 
 input params ( void DoSomething(ref BaseClass object)) but this is not 
 accepted. How can I solve this? Thanx.

What _are_ you doing, anyway?  Why do you need to use .tupleof to do 
polymorphism, why are all your classes templates with empty parameter lists, 
and what does "I want to process all classes derived from base class" mean? 

macky <martin.butina gmail.com> writes:

Jarrett Billingsley Wrote:

 "macky" <martin.butina gmail.com> wrote in message 
 news:evksq3$223e$1 digitalmars.com...
 Hi all!

 I'm trying to figure out how dynamic polymorhism is done the right way in 
 D...

 interface I
 {
    ...some required functions...
 }

 class BaseClass()
 {
    ...implementation of interface...
 }

 class Customer() : BaseClass
 {
   ...some members and overriden baseclass functions...
 }

 class Process()
 {
    void DoSomething(BaseClass object)
    {
        //I want to process all classes derived from base class
    }
 }

 void Main()
 {
   Customer customer = new Customer();
   Process process = new Process();
   process.DoSomething(customer);
 }

 Even though this is working tupleof is not returning any value (I suppose 
 becouse when creating an instance customer is casted in base class and the 
 link is broken - actualy we are dealing with a partial clone).
 Is this the right way of doing things? I know that in c++ you should 

 everything is provided by reference. I tried to provide a "ref" in the 
 input params ( void DoSomething(ref BaseClass object)) but this is not 
 accepted. How can I solve this? Thanx.

 
 What _are_ you doing, anyway?  Why do you need to use .tupleof to do 
 polymorphism, why are all your classes templates with empty parameter lists, 
 and what does "I want to process all classes derived from base class" mean? 
 
 

ah. sorry. Classes are empty due to my lazyness ;). Actualy there are some
virtual methods defined in a base class but some members are are defined just
in a derived class. My idea was that I would get this members with tuppleof
function (I guess I'm trying to fake the reflection). These members do not
exist in a base class ofcourse but my question is if this is possible the way I
wanted to perform this task... Since my DoSomething() function is expecting the
base class and in implementation I have provided the derived class I would
expect that it is handled as a derived class. But I realize that this derived
class is cast in a base class and therefor no member is returned. I would like
to avoid this but I don't know how. I thought that I'm not using input
parameters correctly?

regards, Martin

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"macky" <martin.butina gmail.com> wrote in message 
news:evnbo3$30r2$1 digitalmars.com...
 ah. sorry. Classes are empty due to my lazyness ;). Actualy there are some 
 virtual methods defined in a base class but some members are are defined 
 just in a derived class. My idea was that I would get this members with 
 tuppleof function (I guess I'm trying to fake the reflection). These 
 members do not exist in a base class ofcourse but my question is if this 
 is possible the way I wanted to perform this task... Since my 
 DoSomething() function is expecting the base class and in implementation I 
 have provided the derived class I would expect that it is handled as a 
 derived class. But I realize that this derived class is cast in a base 
 class and therefor no member is returned. I would like to avoid this but I 
 don't know how. I thought that I'm not using input parameters correctly?

 regards, Martin

Ah, I see now.  Depending on what you're trying to do, tupleof might be 
unnecessary.  You could design it the other way around, like so:

class BaseClass()
{
    ...implementation of interface...

    // To be overridden
    void processMe(Process p);
}

class Customer() : BaseClass
{
   ...some members and overriden baseclass functions...
    void processMe(Process p)
    {
        // do the processing
    }
}

class Process()
{
    void DoSomething(BaseClass object)
    {
        // this will call the appropriate process method based
        // on the derived class type
        object.process(this);
    }
}

But that you want to access data fields of classes and not just the methods 
makes me think you want to do something more complex, like .. serializing 
the members of a class to a file?  I'm wondering why you want to access to 
the data fields of the class. 

macky <martin.butina gmail.com> writes:

You're right! Serialization is just one of the benefit comming from this. But
I'm planing to do something even more interesting. I'm trying to port my DAL
(data access layer) into d and share it with d community. I was planning to
bind it to ddbi. From my experiances this is the most convinient way of
handling data in a bussiness application (transaction pattern). Unfortunately
I'm having a hard time accessing fields dynamicaly. I also miss some meta

I embeded tupleof in a class itself (similar to your suggestion) it does not
return it's own fields. *doh*. I'm a bit of stuck here. In order to do what I
have planned I to access fields somehow.

cheers, martin


Jarrett Billingsley Wrote:

 "macky" <martin.butina gmail.com> wrote in message 
 news:evnbo3$30r2$1 digitalmars.com...
 ah. sorry. Classes are empty due to my lazyness ;). Actualy there are some 
 virtual methods defined in a base class but some members are are defined 
 just in a derived class. My idea was that I would get this members with 
 tuppleof function (I guess I'm trying to fake the reflection). These 
 members do not exist in a base class ofcourse but my question is if this 
 is possible the way I wanted to perform this task... Since my 
 DoSomething() function is expecting the base class and in implementation I 
 have provided the derived class I would expect that it is handled as a 
 derived class. But I realize that this derived class is cast in a base 
 class and therefor no member is returned. I would like to avoid this but I 
 don't know how. I thought that I'm not using input parameters correctly?

 regards, Martin

 
 Ah, I see now.  Depending on what you're trying to do, tupleof might be 
 unnecessary.  You could design it the other way around, like so:
 
 class BaseClass()
 {
     ...implementation of interface...
 
     // To be overridden
     void processMe(Process p);
 }
 
 class Customer() : BaseClass
 {
    ...some members and overriden baseclass functions...
     void processMe(Process p)
     {
         // do the processing
     }
 }
 
 class Process()
 {
     void DoSomething(BaseClass object)
     {
         // this will call the appropriate process method based
         // on the derived class type
         object.process(this);
     }
 }
 
 But that you want to access data fields of classes and not just the methods 
 makes me think you want to do something more complex, like .. serializing 
 the members of a class to a file?  I'm wondering why you want to access to 
 the data fields of the class. 
 
 

macky <martin.butina ice.si> writes:

I found a solution, though I'm not sure why things behave like this...
It works if a derived class has its own implementation of GetType(int index) or
GetValue(int index) and base class has only abstract methods of the two. I
would expect if I implement methods in a base class all children would also
implement this method. But it seems that the child class needs to override it
to do the job... yep, tupleof works in a misterious ways ;)


macky Wrote:

 You're right! Serialization is just one of the benefit comming from this. But
I'm planing to do something even more interesting. I'm trying to port my DAL
(data access layer) into d and share it with d community. I was planning to
bind it to ddbi. From my experiances this is the most convinient way of
handling data in a bussiness application (transaction pattern). Unfortunately
I'm having a hard time accessing fields dynamicaly. I also miss some meta

I embeded tupleof in a class itself (similar to your suggestion) it does not
return it's own fields. *doh*. I'm a bit of stuck here. In order to do what I
have planned I to access fields somehow.
 
 cheers, martin
 
 
 Jarrett Billingsley Wrote:
 
 "macky" <martin.butina gmail.com> wrote in message 
 news:evnbo3$30r2$1 digitalmars.com...
 ah. sorry. Classes are empty due to my lazyness ;). Actualy there are some 
 virtual methods defined in a base class but some members are are defined 
 just in a derived class. My idea was that I would get this members with 
 tuppleof function (I guess I'm trying to fake the reflection). These 
 members do not exist in a base class ofcourse but my question is if this 
 is possible the way I wanted to perform this task... Since my 
 DoSomething() function is expecting the base class and in implementation I 
 have provided the derived class I would expect that it is handled as a 
 derived class. But I realize that this derived class is cast in a base 
 class and therefor no member is returned. I would like to avoid this but I 
 don't know how. I thought that I'm not using input parameters correctly?

 regards, Martin

 
 Ah, I see now.  Depending on what you're trying to do, tupleof might be 
 unnecessary.  You could design it the other way around, like so:
 
 class BaseClass()
 {
     ...implementation of interface...
 
     // To be overridden
     void processMe(Process p);
 }
 
 class Customer() : BaseClass
 {
    ...some members and overriden baseclass functions...
     void processMe(Process p)
     {
         // do the processing
     }
 }
 
 class Process()
 {
     void DoSomething(BaseClass object)
     {
         // this will call the appropriate process method based
         // on the derived class type
         object.process(this);
     }
 }
 
 But that you want to access data fields of classes and not just the methods 
 makes me think you want to do something more complex, like .. serializing 
 the members of a class to a file?  I'm wondering why you want to access to 
 the data fields of the class.