[OpenLayers-Dev] constructor signatures

[Bart van den Eijnden]

I agree with Eric.

Best regards,
Bart

On Jun 18, 2010, at 7:17 AM, Eric Lemoine wrote:

> 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
> 
> Camptocamp France SAS
> Savoie Technolac, BP 352
> 73377 Le Bourget du Lac, Cedex
> 
> Tel : 00 33 4 79 44 44 96
> Mail : eric.lemoine at camptocamp.com
> http://www.camptocamp.com
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