[OpenLayers-Dev] constructor signatures

[Eric Lemoine]

On Friday, June 18, 2010,  <christopher.schmidt at nokia.com> wrote:
> On Jun 17, 2010, at 6:33 PM, ext Tim Schaub wrote:
>>     var popup = new OpenLayers.Popup.FramedCloud({
>>         location: xy,
>>         text: text,
>>         closeBox: true
>>     });
>>
>> I think the second form is more readable and less prone to errors.
>>
>> The one argument constructor is nothing new.  We're doing it already in
>> some places in the library.  People coming from popular JavaScript
>> frameworks are comfortable with this.
>>
>> In adding the WMTS layer, I created a constructor that takes a single
>> argument.  If others agree that this is the way forward, I think there
>> is sense in getting used to it before 3.0.
>>
>> I am bringing this up here because Chris objected to my commit of the
>> WMTS layer and reopened the ticket.
>>
>> If anybody else has an opinion about the many versus one argument
>> constructor, please weigh in.
>
> In general, for 2.x, I am supportive of having required
> arguments as seperate parameters, and optional arguments in a single
> object. Some of our existing classes -- popups being a big one :) --
> are obviously not following this convention.
>
> I do not think it is unreasonable to make some things 'required' even
> if they are actually not technically required. In the WMS spec, the
> Title attribute is required, even though there is no technical reason
> why this matters; it simply makes working with layers easier when
> they have names, rather than just positions in an array.
>
> When creating a new subclass, One of the first things that I do is
> compare the Constructor signatures of the parent class to the
> subclass. If the parent has a constructor which is not a 'subset' of
> the child object, it usually means I've done something wrong. In the
> case of Layer, the parent class has:
>
>   Layer(name, options)
>
> My convention for subclasses, then, would be that I could put things
> *between* 'name' and 'options', but that I could not get rid of those
> things; Layer.WMS has:
>
>   Layer(name, params, options);
>
> In all cases I'm aware of (Though I have not examined filters and rules
> extensively, so this may not be true in some portions of the code),
> all of our subclassed items may add things after the 'required'
> parameters, and before the 'options' parameter (which provides a
> space for non-required parameters).
>
> I am comfortable with 'name' being treated as a 'required' parameter
> of layers. I am in favor of maintaining the style of 'extending'
> parameters following this pattern in 2.x; specifically, if a
> parent class declares something 'required', the subclass should
> generally treat it as 'required' (and therefore a seperate parameter)
> unless doing so is significantly painful.
>
> Backing out on something that is one of our few points of consistency --
> Layers require a string as their first argument -- would make me
> sad, but I'm not going to argue that we need to revert a change
> because of it. I just think it's a worthwhile convention to hold onto
> until we really go ahead and change many of our conventions for the
> Glorious Future.
>
> Going forward into 3.x, I am okay with abandoning this convention
> in favor of making everything optional. I don't like it, personally,
> but if this is common Javascript convention, I'm willing to go with
> it.
>
> Apologies if I nitpicked on this one specific feature; I can understand
> that the WMTS layer was likely a lot of work, and am sure that it will
> help many people. I just wanted to comment on the convention change
> because I thought it might actively trip people up.



Hi.


I agree with Chris regarding layer args and consistency.

And I fully support using config objects only in 3.x, with required
options documented as such.

Cheers,

-- 
Eric Lemoine

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