Immutable attributes - part 2

[jrgkraus]

In part one of this post, I described, how to build a class containing public read-only attributes so we can imitate the FINAL attribute concept of JAVA.

Applying this in my daily development work, I came to a slight modification of this approach that uses one class per attribute. To keep the effort low, I use a template (in eclipse ADT) to quickly create such classes.

The immutable one-attribute class

My immutable class now looks like this:

class example_for_string definition.

  public section.

    data value type string read-only.

    

    methods constructor 

      importing value type string.

endclass.



class example_for_string implementation.



  method constructor.

    me->value = value.

  endmethod.



endclass.

In incorporate this in the local definitions of my class. Then I create a private attribute

data example_for_string type ref to example_for_string.

In the constructor (or a different method that is used to initialize the attribute), I instantiate the object with the value, that usually is an import parameter and has the same name. Depending on personal preferences, one would eventually choose to use a prefix for the importing par

me->example_for_string = new #( example_for_string ).

* alternative:

example_for_string = new #( i_example_for_string ).

To speed up the work flow, I created this template in eclipse:

class ${name} definition.

  public section.

    data value type ${type} read-only.

    

    methods constructor 

      importing value type ${type}.

endclass.

* to local implementations

CLASS ${name} IMPLEMENTATION.



  METHOD constructor.

    me->value = value.

  ENDMETHOD.



ENDCLASS.

* to class attributes

data ${name} type ref to ${name}.

* to implementation

me->${name} = new #( ${name} ).

I insert this template (where I have to give only the name and the type of my attribute) in the class-relevant declarations, then move the implementation to "local types" and the other two lines as indicated.

In the code, the immutable attribute can be accessed like this:

if example_for_string->value is initial.