Proper way of changing attributes by class' own methods

[Former Member]

Dear moderators,

this is a generic question which is independent of http://scn.sap.com/thread/3582195, so PLEASE keep this open.

Hello everybody,

I am not sure what is the most appropriate/robust way to change attributes of a class by the class' own private methods - just change them or use a parameter? Simple example:

CLASS sample_class DEFINITION.
     PUBLIC SECTION.
     METHODS main.

     PRIVATE SECTION
     DATA attribute TYPE c.

     METHODS:
     meth1,
     meth2 CHANGING ch_attribute TYPE c.
...
ENDCLASS.

CLASS sample_class IMPLEMENTATION.
     METHOD main.
          me->meth1.
          me->meth2( attribute ).

     METHOD meth1.
          me->attribute = 'X'.
     ENDMETHOD.

     METHOD meth2.
          ch_attribute = 'X'.
     ENDMETHOD.
ENDCLASS.

Would you prefer meth1 or meth2 or does one of the solutions even raise problems that I don't see? Of course, if a method changes lots of attributes it is impractical to use parameters, but besides that?

created by Tomas Buryanek in ABAP Development

---

Difference would be third method:

     set_attribute IMPORTING i_value TYPE c.

...

     METHOD set_attribute.

          me->attribute = i_value.

     ENDMETHOD.

...

lo=>set_attribute( 'A' ).

which is example of classic "setter" method.

For this topic check theory and usage of encapsulation OOP principle. It will help understand

[Former Member]

So Tomas, do I get you right that you would set up a set_attribute method for each single attribute of a class (if it needs to be changed by methods of the class)?

You are right, I have to get a bit more familiar with the concepts, but this is a part of that 😉

[matt]

I only put setters and getters on public attributes, if I need r/w or write access to them. For private, protected and read-only attributes, I use the attribute directly.

[Tomas_Buryanek]

No, I realized your question is little bit different so I deleted my (little bit confusing) answer in old topic.

I would say that all 3 methods are ok, but each is for different usage...

[Former Member]

Hm, if you are using get/set methods for an attribute anyway, why not make this attribute private? Your suggestion seems a little inconsistent to me, as a public attribute with associated get/set methods could still be changed directly, which is against the intention of get/set methods...

Just to recall, my question is about changing (not reading) attributes of a class by the class' own methods (not from outside).

[Former Member]

Could you please explain your thoughts about the different usage in a bit more detail? 🙂

[Tomas_Buryanek]

I can try describe methods by how i see them (method naming can help a lot)

meth1 => do_something( )

its like for example your method main( )...

meth2 => do_something_with( attribute )

if you have some logic which could be called multiple times with different attributes...

meth3 => set_attribute( value )

classic "setter", class with them can be very robust (which can be contraproductive), for example you can encapsulate validation of value inside...

[matt]

Sorry, that was badly expressed. I should say

I use the attributes directly if they're read-only public, private or protected. Otherwise, I set them as private or protected, and use getters and setters. I do not use non-read-only public attributes.