#when:send:to:

> On Fri, 13 Nov 2015 12:58:22 -0500
> "Dan Norton" <[hidden email]> wrote:
>
> > Hello Everyone,
> >
> > The following repo contains before and after examples of replacing
> the Dependency
> > Mechanism with the Observer Pattern:
> >
> > https://github.com/dhnorton/Cuis-Smalltalk-light
> >
> > Please take a look at this and tell me what needs to change.
>
> Dan,
>
> Good start.
>
> I would suggest a deeper example.
>

> Lights could be a model with a presenter (LightPanel) which shows
> the lights.  E.g. open a layout morph with a row of elipses
> (circles) which are red/green (or whatever) for off/on.
>
> Clicking on a light changes the model (Lights subclass ActiveModel),
> which signals
>   triggerEvent: #colorChange with: aColor.
>
> You can look in Morphic-Misc1 at RadioButtonMorph to see how to
> handle clicks.
>
> Workspace code could also turn off/on or just toggle lights in the
> model, with the LightPanel presenter updating appropriately.
>
> One can then add a bit of wackyness, like using different colors
> than red/green and the presenter will show the proper color..
>
> $0.02.
> -KenD
>
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> Hello Everyone,
>
> The following repo contains before and after examples of replacing the Dependency
> Mechanism with the Observer Pattern:
>
> https://github.com/dhnorton/Cuis-Smalltalk-light
>
> Please take a look at this and tell me what needs to change. I'm trying to supply an example
> of the Observer Pattern so that others might use #when:send:to: with less difficulty than I
> experienced. There may be better examples but I picked one from the Blue Book.
>
> It seems that #when:send:to: is necessary but not sufficient as a replacement for the
> Dependency Mechanism. In this example, it replaced #addDependent:, not #changed or
> #update and I am still not comfortable with how to choose the parameters. This may be an
> example of the difficulty in explaining the obvious, I'm not sure :-)
>
> The #changed method was replaced with #triggerEvent: with a symbol argument which is
> referred to in one of the arguments of #when:send:to: and that's the only constraint AFAICT.
>
> The #update: method was retained, as a convenience; it also needs to agree with one of the
> arguments of #when:send:to: and could have been different.
>
> Please tell me if any of this is wrong. Thanks.
>
>   - Dan

> Hi Dan,
>
> On 13/11/2015 02:58 p.m., Dan Norton wrote:
> > Hello Everyone,
> >
> > The following repo contains before and after examples of replacing
> the Dependency
> > Mechanism with the Observer Pattern:
> >
> > https://github.com/dhnorton/Cuis-Smalltalk-light
> >
> > Please take a look at this and tell me what needs to change. I'm
> trying to supply an example
> > of the Observer Pattern so that others might use #when:send:to:
> with less difficulty than I
> > experienced. There may be better examples but I picked one from
> the Blue Book.
> >
> > It seems that #when:send:to: is necessary but not sufficient as a
> replacement for the
> > Dependency Mechanism. In this example, it replaced #addDependent:,
> not #changed or
> > #update and I am still not comfortable with how to choose the
> parameters. This may be an
> > example of the difficulty in explaining the obvious, I'm not sure
> :-)
> >
> > The #changed method was replaced with #triggerEvent: with a symbol
> argument which is
> > referred to in one of the arguments of #when:send:to: and that's
> the only constraint AFAICT.
> >
> > The #update: method was retained, as a convenience; it also needs
> to agree with one of the
> > arguments of #when:send:to: and could have been different.
> >
> > Please tell me if any of this is wrong. Thanks.
> >
> >   - Dan
>
> I think the idea of #when:send:to: is to use event names and actions
> that make sense to your model (and not #changed and #update:). For
> instance, in Example2>>#lights:, I would change the line:
>
>          eachLight when: #changed send: #update: to: dependentLight
> with: self
>
> to read:
>
>          eachLight when: #turnedOn send: #turnOff to:
> dependentLight
>
> And, in #turnOn, make it do:
>
>          self triggerEvent: #turnedOn
>
>
> Doesn't this read better?
>

> On 16 Nov 2015 at 21:11, Juan Vuletich wrote:
>
>> Hi Dan,
>>
>> On 13/11/2015 02:58 p.m., Dan Norton wrote:
>>> Hello Everyone,
>>>
>>> The following repo contains before and after examples of replacing
>> the Dependency
>>> Mechanism with the Observer Pattern:
>>>
>>> https://github.com/dhnorton/Cuis-Smalltalk-light
>>>
>>> Please take a look at this and tell me what needs to change. I'm
>> trying to supply an example
>>> of the Observer Pattern so that others might use #when:send:to:
>> with less difficulty than I
>>> experienced. There may be better examples but I picked one from
>> the Blue Book.
>>> It seems that #when:send:to: is necessary but not sufficient as a
>> replacement for the
>>> Dependency Mechanism. In this example, it replaced #addDependent:,
>> not #changed or
>>> #update and I am still not comfortable with how to choose the
>> parameters. This may be an
>>> example of the difficulty in explaining the obvious, I'm not sure
>> :-)
>>> The #changed method was replaced with #triggerEvent: with a symbol
>> argument which is
>>> referred to in one of the arguments of #when:send:to: and that's
>> the only constraint AFAICT.
>>> The #update: method was retained, as a convenience; it also needs
>> to agree with one of the
>>> arguments of #when:send:to: and could have been different.
>>>
>>> Please tell me if any of this is wrong. Thanks.
>>>
>>>    - Dan
>> I think the idea of #when:send:to: is to use event names and actions
>> that make sense to your model (and not #changed and #update:). For
>> instance, in Example2>>#lights:, I would change the line:
>>
>>           eachLight when: #changed send: #update: to: dependentLight
>> with: self
>>
>> to read:
>>
>>           eachLight when: #turnedOn send: #turnOff to:
>> dependentLight
>>
>> And, in #turnOn, make it do:
>>
>>           self triggerEvent: #turnedOn
>>
>>
>> Doesn't this read better?
>>
> +2
> ...because yes, it reads better, but there's more:
>
> #when:send:to: replaces #when:send:to:with:
>
> in Light2, #update: goes away, with a little factoring
>
> The #triggerEvent: arg is changed to #turnedOn. This is elegant.
>
>   - Dan
>