Another reason is that there could be a nil in your collection, by design or not, so that returning nil on not found would result in both of these
(OrderedCollection with: nil) detect: [ :each | each isNil ] ifNone: [ nil ].
(OrderedCollection with: #somethingElse) detect: [ :each | each isNil ] ifNone: [ nil ].
being nil, so that you don't know the answer to what you want to know.
On 16 Oct 2012, at 20:40, Mariano Martinez Peck <
[hidden email]> wrote:
> On Tue, Oct 16, 2012 at 7:46 PM, sergio_101 <
[hidden email]> wrote:
> i had a problem earlier, thinking that if i did a detect: on an
> ordered collection, and the item was not found, i would get back nil.
> it turns out that it throws an error..
>
> to get this to work, you use:
>
> detect:ifNone:
>
> my only question is... why is this so?
>
> what is the motivation behind throwing an error rather than returning nil?
>
> i guess i would like to understand the 'smalltalkiness' about this,
> just in case i run into something like this in the future..
>
>
> Smalltalk tries to be explicit and not to put things under the carpet. So in this case, it will throw an exception instead of returning nil.
> If that is what you want, then you can always do detect: [ ... ] ifNone: [ nil ] and you will get the behavior you want.
> So, forget for a moment all you background of any programming language you have, why would you expect to return nil? ;)
> Anyway, we have to admit, there still places in Smalltalk where we return nil instead of throwing an exception.
>
> thanks!
>
> ----
> peace,
> sergio
> photographer, journalist, visionary
>
>
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> --
> Mariano
>
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Sven Van Caekenberghe
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