是否可以在 abap OO 中实现 REJECT？

Question

Is it possible to implement the idea below? The idea is that it works pretty much as a REJECT from the GET statement, but inside the OO paradigm.

start-of-selection

    lv_max_lines = class1->get_max_lines( ).

    do lv_max_lines.
        class2->method1( class1->get_line_by_index( sy-index ) ).
    enddo.


class 2 implementation.

    method method1.
        method2( is_line ).
    endmethod.

    method method2.
        method3( is_line ).
    endmethod.

    method method3.
        if ls_line <> what_I_need.
            class1->reject( ). "or
            class1->reject( is_line ).
            "go back straight to start of selection and execute next iteration,
            "ignoring the rest of method3 and metho2 and method1 from class2.
        endif.
        "more process
    endmethod.

endclass.

Surely it can be done with multiple conditions in class2 methods and return statements, but the idea would be to simulate a reject which doesn't require the class2 to have any modifications, the whole job would be left to class1 to handle.

One idea I had was to delete the current line from the class1 table that is being accessed, that would not work as expected, in fact, I am not sure how this would work.

I think this is not possible to achieve, but I'd like to give it a try regardless.

Answer 1

Yes, it is possible through class-based exceptions inheriting from class CX_NO_CHECK .

" inherit cx_no_check to let the exception bubble upwards
" without having to redeclare it
class bad_input definition inheriting from cx_no_check.
endclass.

start-of-selection

  lv_max_lines = class1->get_max_lines( ).

  do lv_max_lines times.
    try.      
        class2->method1( class1->get_line_by_index( sy-index ) ).
      catch bad_input.
        " do nothing, just continue with the next line
    endtry.
  enddo.

class class2 definition.
  public section.
    methods method1 importing is_line type whatever.
  private section.
    methods method2 importing is_line type whatever.
    methods method3
      importing
        is_line type whatever.
endclass.

class class2 implementation.

  method method1.
    method2( is_line ).
  endmethod.

  method method2.
    method3( is_line ).
  endmethod.

  method method3.
    if ls_line <> what_I_need.
      raise exception new bad_input( ).
    endif.
    "more process
  endmethod.

endclass.