Exception as flow control?

[Ashish Malik]

I want to execute certain methods linearly in a way that if any of the methods says the data passed to it is invalid, it should not let methods to be called after it to execute.
For example, my code has following calls:

validateA(someData);
validateB(someData);
validateC(someData);

If validateB() says 'someData' is invalid then validateC() should not execute. What can be a good solution to that? (Probably without using exception as flow control!)

[Darryl Burke]

What's the return type of those three methods?

[Ashish Malik]

I have, for now, had it to be boolean so that i could make:

if(validateA()){
if(validateB()){
validateC()
}
}

This didn't seem a good solution to me!

[Matthew Brown]

You could argue that since you're actually checking for errors, using exceptions here is actually appropriate. I might well take that approach.

If you're not convinced by that, then you can avoid deep nesting of methods by taking advantage of the fact that && short-circuits:

boolean isOk = true;
isOk = isOk && validateA();
isOk = isOk && validateB();
isOk = isOk && validateC();
...

Edit: having seen Jesper's post below, I'd just add: I'd use my approach for many validations, or if I thought the number was likely to change. If I was confident there were always going to be a small number, I'd use his.

[Jesper de Jong]

Or just:

if (validateA() && validateB() && validateC()) {
// ...
}

This guarantees that for example validateB() and validateC() will not be called if validateA() returns false, because expressions are evaluated from left to right and && is a short-circuit operator (if the operand on the left is false, it won't evaluate the operand on the right).

[Winston Gutkowski]

 

Ashish Malik wrote:If validateB() says 'someData' is invalid then validateC() should not execute. What can be a good solution to that?

As you can see, there are several possibilities.

One other thing to consider is: are these validations independent? If they are, then all the advice given so far is absolutely correct. If they aren't, you may need to consider writing your methods differently, eg:

public boolean validateA() {
// validation code
return validateB();
}
public boolean validateB() {
// validation code
return validateC();
}
public boolean validateC() {
// validation code
return valid;
}

would imply that your three methods have a hierarchy.

Winston

[Ashish Malik]

As all validations are independent i would fallback on

if(validateA() && validateB() && validateC())

Thanks!