Re: Throw Exceptions from setters: second opinion

amygdala wrote:
Op Tue, 30 Dec 2008 15:34:18 +0100 schreef Jerry Stuckle <jstucklex@xxxxxxxxxxxxx>:

amygdala wrote:
Op Tue, 30 Dec 2008 13:16:16 +0100 schreef Jerry Stuckle <jstucklex@xxxxxxxxxxxxx>:

amygdala wrote:
Hi all,
Recently somebody on a forum told me, and nearly convinced me, that throwing Exceptions from setters is bad practice. He stated that setters should only return boolean false if the provided input is not valid, since that is what they are expected to do: validate input and simply tell wheter it's valid or not. Furthermore he stated that throwing Exceptions is only meaningful when an internal routine of the class encounters invalid data. Does this sound reasonable to you? I'm not sure yet myself. Love to hear your opinions on the matter.
Thanks in advace.

Not at all. It's actually quite a good idea to throw exceptions from setters.

Returning true/false from a setter is old school - from before the time exceptions existed. Nowadays, a better way is to return the value you are setting it to. That way you can chain operations.

A 'fluid interface' you mean? Yes it makes sense now.
Because this way you now could do something like the following:
try
{
$myObject->setSomething( $something )
->setAnotherThing( $anotherThing )
->tellMyObjectToTakeAction()
}
catch( MyObjectException $exception )
{
// act on the caught Exception
}
... in stead of the very verbose:
if( myObject->setSomething( $something ) )
{
if( $myObject->setAnotherThing( $anotherThing ) )
{
if( !$myObject->tellMyObjectToTakeAction() )
{
// act on return value false of tellMyObjectToTakeAction()
}
}
else
{
// act on return value false of setAnotherThing()
}
}
else
{
// act on return value false of setSomething()
}
...right?

Yes, that is called "chaining operations", not a "fluid interface".


Yes, that's why I put it in between quotes. Because that is how I've seen it being called (Zend Framework, etc) in stead of chained operations. Never seen the term chained operations before as far as I can recall.

I first saw it about 25 years ago when I was learning C. It's very common to chain operations in C.

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==================
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@xxxxxxxxxxxxx
==================
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Relevant Pages

  • Re: Throw Exceptions from setters: second opinion
    ... He stated that setters should only return boolean false if the provided input is not valid, since that is what they are expected to do: validate input and simply tell wheter it's valid or not. ... Furthermore he stated that throwing Exceptions is only meaningful when an internal routine of the class encounters invalid data. ... // act on return value false of tellMyObjectToTakeAction ...
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  • Re: Throw Exceptions from setters: second opinion
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  • Re: Throw Exceptions from setters: second opinion
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  • Re: Throw Exceptions from setters: second opinion
    ... He stated that setters should only return boolean false if the provided input is not valid, since that is what they are expected to do: validate input and simply tell wheter it's valid or not. ... Furthermore he stated that throwing Exceptions is only meaningful when an internal routine of the class encounters invalid data. ... // act on return value false of tellMyObjectToTakeAction ...
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