[Newbies] anObject select: #aMethodName -- is this good Squeak?

Ron Teitelbaum Ron at USMedRec.com
Wed Feb 7 18:42:15 UTC 2007

Hi Michael,

It's a trick.  It only works because #value: is implemented on symbol as: 

Symbol>>value: anObject
	^anObject perform: self.

So the following works too.

#asUppercase value: 'I am a trick'

My suggestion is that you shouldn't follow such tricks.  Although I do it
too sometimes with things like.

aDictionary at: #foo ifAbsent: nil.

Since nil responds self to #value it seems redundant to me to put the nil in
a block so that it can return nil when the block is evaluated with #value.
Even though in this case the execution is faster but in the case of sending
a symbol to select it is slower.

In both cases it is harder to read so in my opinion it is best to stick with
arguments that are expected.

Ron Teitelbaum

> From: Michael Davies
> Sent: Wednesday, February 07, 2007 1:07 PM
> I was browsing some of the Magritte source code, when I saw a message
> that confused me:
> 	selectors := anObject class allSelectors
> 		select: #isDescriptionSelector.
> I couldn't understand how you could pass a Symbol to #select: instead
> of a block -- certainly the definition of Collection>>select: implies
> it should only take a block. But trying it for myself, I see it works
> -- eg
> { 1. 2. 3. 4. } select: #even.
> can be used in place of:
> { 1. 2. 3. 4. } select: [ :each | each even ]
> Given how much simpler this looks, I was surprised I'd not seen this
> usage before, and searching for senders of #select: shows that the
> wordier version seems to be generally preferred.
> So my question is: is this a usage I should adopt or avoid?
> Cheers,
> Michael
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