On 22 mai 2014, at 19:46, sergio_101 <sergio.rrd@gmail.com> wrote:

In many cases, an object might have a method (filter, selector, etc) attached to it so that the object can run the correct method..

for instance, an object might have a filterMethod variable with a value 'filterByArtist'..

in ruby, i would do something like:

instance.send(filter_method)

how would i do that in pharo, and is this a bad idea?

"instance perform: filterMethod asSymbol" If filterMethod is already a symbol you can omit asSymbol. It is slower than regular message send but it's also the safest reflective operation since it's the only one that doesn't break object encapsulation.

thanks!

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Hi! On Thu, May 22, 2014 at 7:46 PM, sergio_101 <sergio.rrd@gmail.com> wrote:

In many cases, an object might have a method (filter, selector, etc) attached to it so that the object can run the correct method..

for instance, an object might have a filterMethod variable with a value 'filterByArtist'..

in ruby, i would do something like:

instance.send(filter_method)

how would i do that in pharo,

Selectors (method signatures) in Pharo are represented with Symbols, not Strings. In order to send a message from a given symbol you can do: object perform: #symbol or object perform: #symbol: with: anArgument or object perform: #symbol: withArguments: anArrayOfArguments for example 2 perform: #even. 2 perform: #+ with: 3

and is this a bad idea?

It usually depends on what you want to achieve... You can also reach the same result having two filter objects: NullFilter>>filter: aCollection ^ aCollection ByArtistFilter>>filter: aCollection ^ aCollection select: [ :each | each artist = myArtist ] And you can even think about a third solution with blocks describing the filters. Making them objects to me gives you more power. They are objects, you can manipulate them, compose them, etc. Blocks can capture variables from the scope, but they are a bit obscure (as symbols are too).

thanks!

-- ---- peace, sergio photographer, journalist, visionary #BitMessage BM-2D8VWUJSS41RFKh1ec83preVabHrnniExa

http://www.Village-Buzz.com http://www.ThoseOptimizeGuys.com http://www.CodingForHire.com http://www.coffee-black.com http://www.painlessfrugality.com http://www.twitter.com/sergio_101 http://www.facebook.com/sergio101