Getting rid of if-else and switch in c++

Question

I have these long if - else/switch statements, really long, and they make the code hard to read. So was just wondering is there a way to get rid of them? Maybe something like using a class for each condition and then using chain of responsibility pattern ?

What kind of approach would you suggest ?

Here is a sample code:

    if (  cc == LIB_DEFINED_CONSTANT_1  )
    {

        response = "-1";

        errorWindow->setText ( "The operation timed out.\nPlease try again later." );
        errorWindow->show (  );

    }   

    else if (  cc == LIB_DEFINED_CONSTANT_2  )
    {

        response = "-1";

        errorWindow->setText ( "Couldn't conect to the server.\nPlease try again later." );
        errorWindow->show (  );

    }

    else if (  cc == LIB_DEFINED_CONSTANT_3  )
    {

        response = "-1";

        errorWindow->setText ( "Access is denied.\nPlease contact our support team." );
        errorWindow->show (  );

    }

    else if (  cc == LIB_DEFINED_CONSTANT_4  )
    {

        response = "-1";

        errorWindow->setText ( "Credentials and varified\nPlease contact our support team." );
        errorWindow->show (  );

    }
    else if ....

As you can see, most of the code in the conditional tag is some what similar, except for setting text for errorWindow.

EDIT : It would be nice if people can leave comment on why they down voted.

It depends on what problem they solve, but it's probably something that can be resolved with an array, a map or a state machine. — Morwenn, Jun 27 '13 at 09:25
Who knows... without seeing the code or at least a more comprehensive explanation as to what the conditions being tested are and what code is being executed in each controlled block. — CB Bailey, Jun 27 '13 at 09:27
Without code, I have no idea. Put a minimal sample in your question, with say 2 or 3 of your conditions. Whithout more context you won't get much of an answer. — rectummelancolique, Jun 27 '13 at 09:27
This might be a useful starting point http://stackoverflow.com/questions/505454/large-switch-statements-bad-oop?rq=1 — Marcello Romani, Jun 27 '13 at 09:34
In your example, you are duplicating _everything_ except the contents of a string. Start by eliminating duplication, i.e. factoring out lines which are exactly the same to a single place. You'll be left with a table of error codes and string descriptions, and you'll be able to tackle _that_ specific problem. — Daniel Daranas, Jun 27 '13 at 09:47
I think this question would be better placed at http://codereview.stackexchange.com , because the code is working in the way it should (as far as I can see from your question), and you're asking for suggestions for improvement. I think @DanielDaranas has given the most useful hint so far: store the error codes in one array (preferably `std::vector`), and the corresponding error messages in another array (`std::vector`), or create a `struct` containing error code and message, and put all of them into an array. The details are left as an exercise to the reader ;) — Piotr99, Jun 27 '13 at 11:58

score 2 · Answer 1 · answered Jun 27 '13 at 09:30

2

In general, you should try to split your code into small functions/methods, and each of them should do exactly one thing. If you have a very long (several pages) if/else block, you should probably refactor your code.

I think that code should read like this:

if (shouldIdoThing1()) 
{
  doThingOne(withThis, andThis, andThat);
}
else if (shouldIdoThing2())
{
  doTheSecondThing(withThisOnly);
} 
else
{
  doTheOtherThing(withSomethingElseEntirelyPerhaps);
}

and, if possible, I try to make my code look like that. In large applications scrolling through several pages just to check what is done in else is a real pain in ... one's head.

answered Jun 27 '13 at 09:30

Dariusz

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I think this isn't addressing the question, as it specifically asked to get rid of the if/else statements. – Piotr99 Jun 27 '13 at 12:01
@Piotr99 he wants to get rid of "really long" statements which "make the code hard to read". My answer addresses these issues. – Dariusz Jun 27 '13 at 12:58

Getting rid of if-else and switch in c++

1 Answers1