smalltalk - instantiate an object with parameters..

yes, i know this sounds simple.. but is it possible to instantiate an
object with some parameters?

say i have a dictionary:

params := Dictionary new.
params at: 'sound' put: 'bark'

dog := Dog new.

^^ at this point, i would like to just create a dog and send it
'params' all at once..

can i do this? what would the syntax look like?

thanks!


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On 2012-09-11, at 20:36, sergio_101 <[hidden email]> wrote:

sure :) in Smalltalk (almost) everything is a message-send :)

So you can do the following:

dog := Dog sound: 'wuff'.

then a class side method:

Dog class >> #sound: aString
        ^ self basicNew
                initializeWithSound: aString.

then the initializeWithSound: methods on instance side

Dog >> #initializeWithSound: aString.
        self initialize.
        "now do the special initialization here..."
        " for instance set the sound"
        sound := aString.

Dog >> initialize
        "do the default initialization here"
        "for instance set a default sound"
        sound := 'bark'.


Hope that helps :)
       

Hmm... there's no "magic" for this. 

On 2012-09-11, at 20:50, Benjamin <[hidden email]> wrote:
well initialize.* usually returns self :) (it's like #initialize, where you never send #yourself)

> Dog class>>newWithParams: aDictionary
>    ^self new params: aDictionary
>
> Dog>>params: aDictionary
> params := aDictionary
>
> Is that something similar to what you were looking for?
>

yes! this is very close to what i am looking to do.. this is kind of
where i figured it was going to go..

i was hoping it would be a one liner.. but i can live with this..

thanks!

--
----
peace,
sergio
photographer, journalist, visionary

http://www.ThoseOptimizeGuys.com
http://www.CodingForHire.com
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If you actually wanted to just set the sound of the dog, and you don't really need a Dictionary, you can do:

In Smalltalk you could do that, with any class side constructor or with a builder class.

If you're looking for something more similar to how some JavaScript constructors work, where you can map property names of an anonymous object to properties of the new instance then there is no such feature, but I guess you could build it more or less easily passing a dictionary as argument.

Ie. JavaScript:
Object.create(Dog.prototype, {
    sound: 'bark',
    pitch: 1.1,
    filterFunction: function(s){...}
})

And then have a Dog instance with sound, pitch and filterFunction copied from the second argument.
 

Ie. Smalltalk
Dog fromDictionary: (Dictionary new
            at: #sound put: 'bark';
            at: #pitch put: 1.1;
            at: #filterFunction put: [:s | ];
            yourself).


And then map the keys in the dictionary to methods, properties or instance variables of your new Dog instance.

Kind of hacky for Smalltalk, but useful in JS due to its prototypical essence.

Not having a hash/dictionary literal syntax makes its use counter-intuitive and too verbose.
I'd rather use my own constructor, maybe it will take a little longer but in the long term the explicit selector will make its semantics more clear.

Regards,

--
Esteban.

On Sep 11, 2012, at 8:52 PM, Camillo Bruni wrote:

Play with Morphic and then you will take this habit too :)

Ben

>
> But I don't really know what were you using that dictionary for and what was
> the intention (#params: is not a very nice name).
>

i have been intentionally being vague about what i am doing, as i am
trying to understand the best smalltalk practice, without introducing
an approach from another language.

the idea i am after is something like this in rails..

i can make a hash like:

dog_params = {:sound => 'bark', :food => 'steak'}

and create a dog like:

Dog.create(dog_params)

and have a dog that with those params..

i just want to make sure i am not inventing a problem to solve.. and
that there isn't a more 'smalltalky' way to do it.

thanks!



--
----
peace,
sergio
photographer, journalist, visionary

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

On 09/11/2012 12:28 PM, sergio_101 wrote:
> i have been intentionally being vague about what i am doing, as i am
> trying to understand the best smalltalk practice, without introducing
> an approach from another language.


This is a good guide:

http://www.amazon.com/Smalltalk-Best-Practice-Patterns-Kent/dp/013476904X

>
> This is a good guide:
>
> http://www.amazon.com/Smalltalk-Best-Practice-Patterns-Kent/dp/013476904X
>

i actually just bought that, and am making my way through it now..

thanks!

--
----
peace,
sergio
photographer, journalist, visionary

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

sergio_101 wrote

>
> But I don't really know what were you using that dictionary for and what was
> the intention (#params: is not a very nice name).
>
i have been intentionally being vague about what i am doing, as i am
trying to understand the best smalltalk practice, without introducing
an approach from another language.

the idea i am after is something like this in rails..

i can make a hash like:
dog_params = {:sound => 'bark', :food => 'steak'}

and create a dog like:
Dog.create(dog_params)

and have a dog that with those params..
i just want to make sure i am not inventing a problem to solve.. and
that there isn't a more 'smalltalky' way to do it.

There is no other way to do what you want except using a dictionary/collection/etc.

They keywords in Smalltalk must preserve the order because they're part of the method name, not its arguments.

You could build your own way of passing "dynamic" parameters to the constructor, but most of the times if you need too many arguments for a constructor you might be needing to introduce a new abstraction, so take it as a sign to reify something.

Syntax sugar in Smalltalk most of the times comes from better abstractions, not from the language's syntax.

Regards,

--
Esteban.

This small (really small and useful) book could help you with your style

>
> You could build your own way of passing "dynamic" parameters to the
> constructor, but most of the times if you need too many arguments for a
> constructor you might be needing to introduce a new abstraction, so take it
> as a sign to reify something.

thanks, esteban.. this is exactly where my sixth sense was taking me..

--
----
peace,
sergio
photographer, journalist, visionary

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

read Smalltalk by Example book of alec sharp

Stef

On Sep 11, 2012, at 8:36 PM, sergio_101 wrote: