如何重用稍有不同的代码

Question

I'm having some difficulties about how to correctly design and implement two methods.

I have 2 methods, A and B. Method A does 2 things and method B does only 1 thing. One of the things that method A does is the same as what method B does, so it is very reasonable to call method B from within a method A.

Now the problem is that both methods need to send exactly one email to a user. When I invoke A, I want to receive 1 email and when I invoke B, I also want to get 1 email. This means that if I call method B inside A, I will now get 2 mails while doing 1 action (= invoking A). To make it even more tempting to simply include B in A, the set up procedure is truly the same for both methods and so instead of redoing the set up in the B, I could simply call method B with these set up data from A. But I have no setup data to provide when calling the B directly and so in this case I'd need to do the setup anyway.

What is the best approach to solve such a problem? Should I:

1. Add a parameter to method B in which I will say whether it should send the email or not and another parameters for the setup data
2. Keep the two methods separated, because method B is not doing exactly the same thing in the two contexts
3. ... other suggestions?

PS. I'm not sure if stackoverflow is actually suitable for such a question, let me know if there's a better stackexchange platform for this.

Thanks for any ideas

Answer 1

I don't know if this is truly on-topic either. That said...

It seems to me that "sending email" is one of the things that is included in the method B work that method A needs done. As such, why not just implement it in method B? Then method A gets it for free when it calls method B.

If the exact contents of the email are different depending on whether method A was called or not, then sure…you can add a parameter to method B to customize the email in some way.

Finally, you're pretty vague on the details. It's not really clear just how much code you're saving by calling method B from method A. If it's significant, then I'm a strong proponent of code sharing like this. But if we're just talking a single statement, well...that seems less worth bothering with; maybe just putting that same single statement in each method is better.

Sorry for the vague answer. GIGO. :)

Answer 2

You could use the return of the methods for the content of our email:

private String funcA() {
    // foo
    return "Mail from funcA";
}

private String funcB() {
    funcA();      // ignoring the return value here, we later return our on
    // foo
    return "Mail from funcB";   // our own return
}

Then you send the email outside of these functions (JUST EXAMPLE CODE):

private void mainFunc() {
    String mail = condition ? funcA() : funcB();

    sendMail(mail);
}

Answer 3

I have two ideas:

• create C method that represents common functionality of A and B, and invoke C in A and B with different parameters
• invoke B inside A, but extract mailing functionality alone to separate method C

To clarify the first idea:

methodA() {
        firstAction();
        secondAction(Parameter parameterFromA);
        }

methodB() {
        secondAction(Parameter parameterFromB);
        }

Answer 4

I would suggest you split out the functionality a little further.

Currently you have two methods that might be described something like this:

void MethodA()
{
    DoThing1();
    DoThing2();
    SendEmail();
}

void MethodB()
{
    DoThing1();
    SendEmail();
}

So one fairly simple answer is to extract the actual functional bits out of the two methods into methods of their own and leave behind a shell similar to the above. Each of the DoThingX methods can return whatever it is you need for building the email, etc.

Of course if the DoThingX methods are really small - a couple of lines or so, for instance - then it might not make sense to break them out this way.