CHECK vs. RETURN

[nomssi]

CHECK vs. RETURN

[HrFlorianHoffmann]

While the statement's name CHECK does describe that it evaluates a condition, it unfortunately does not hint at what happens if the condition fails.

Previous discussions suggested that the ABAP community would prefer a name like:

RETURN IF <condition>.

[ilyakaznacheev]

CHECK is a beautifully self-describing statement - it does exactly that - checks some condition.
From my perspective, it's ok to use it to execute some initial consistency checks, like empty parameters, validation, etc.

But it's not ok to interrupt the method in other cases.

[fabianlupa]

I like CHECK as the first statement in BAdI implementations. For example to check if the implementation should be called in the current client.

[nomssi]

To make my point clear: I promote the use of CHECK in a functional method. In this use case, it should not be the first Statement of the method.

[marcellourbani]

IMHO depends on context

A check in the middle of a very long method is frowned upon because it interrupts the flow and is hard to spot.
I agree, but that's mostly a consequence of the method being too long.
In a short one is not a big deal IMHO
At any rate, I will always favour

check a is not initial.

over

if a is initial.
  exit. " or return when equivalent
endif.

The argument about the statement name is not an issue for ABAP developers. Has some merit when a colleague looks at our code

[drakth]

While CHECK is useful in some cases, as people said before, I usually suggest to avoid using it inside LOOPs where the CHECK is used but could be replaced with a LOOP WHERE.

[nomssi]

I see this In the context of methods, outside LOOPs as in "Replace Nested Conditional with Guard Clauses" (cf. Refactoring (c) 1999 by Martin Fowler:

conditional expressions have different intentions: The first form is a check whether either course is part of the normal behavior. The second (called a guard clause) is for a situation in which one answer .. is normal behavior, the other an unusual condition.

[f4abap]

Check is something which should never be used in my eyes. Doesn't make sense to me. When I have methods and other stuff done very small (3 to 5 lines only) where is the argument to use a check... a if-condition works always fine.. as stated by @HrFlorianHoffmann a few comments above.

[nomssi]

CHECK outside of LOOP is mostly used as the first statement in a method. This is an established pattern to enforce the method contract. The extended syntax check will not complain in this case.

Now another usage of CHECK outside LOOPs, verbatim from ABAP Scheme:

CLASS lcl_lisp_number DEFINITION INHERITING FROM lcl_lisp ABSTRACT.
    PUBLIC SECTION.
      METHODS is_exact RETURNING VALUE(result) TYPE REF TO lcl_lisp.
      METHODS is_inexact RETURNING VALUE(result) TYPE REF TO lcl_lisp.
      DATA exact TYPE flag READ-ONLY.
  ENDCLASS.

  CLASS lcl_lisp_number IMPLEMENTATION.

    METHOD is_exact.
      result = false.
      CHECK exact EQ abap_true.
      result = true.
    ENDMETHOD.

    METHOD is_inexact.
      result = true.
      CHECK exact EQ abap_true.
      result = false.
    ENDMETHOD.

  ENDCLASS.