[swift-evolution] [Proposal] Sealed classes by default

[Michael Ilseman]

If “opened”, who or what did the opening? If “open” is like “extensible”, then I would interpret “opened” to be like “extended”.

> On Jul 1, 2016, at 10:35 AM, Leonardo Pessoa via swift-evolution <swift-evolution at swift.org> wrote:
> 
> The proposal was to use "sealed" so why not "opened"? I understand it
> may not be common to use "opened" as an adjective but from the
> dictionaries I consulted it is possible to.
> 
> opened class MyViewController: UIViewController {
>       opened func displayMe(_ me: person) { … }
> }
> 
> On 1 July 2016 at 13:47, John McCall via swift-evolution
> <swift-evolution at swift.org> wrote:
>> On Jul 1, 2016, at 12:23 AM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>> That starts to look an awful lot like a fifth access level just for classes
>> (I know you're not proposing one, but it could start to look that way to a
>> user). I think there's much to be said for having the word public in front
>> of things that are public. Unless, of course, your strawman keyword is a
>> much maligned compound word that begins with "public", like
>> "publicoverridable".
>> 
>> 
>> I would also prefer a single keyword if the word implies something about
>> accessibility.  "open" does that, although using it here would conflict with
>> its potential use on enums unless we required all cases within the defining
>> module to be present in the enum declaration rather than extensions.
>> 
>> I don't think we'd ever use a compound keyword that starts with public; we'd
>> just separate them and say that the second half can only be present on a
>> public declaration, or do this parenthesized syntax.
>> 
>> John.
>> 
>> 
>> On Fri, Jul 1, 2016 at 01:54 Brent Royal-Gordon <brent at architechies.com>
>> wrote:
>>> 
>>>> If we're going to go along those lines, we should just use
>>>> public(subclassable) and public(overridable).  We can fall back on those if
>>>> necessary; I would just like to continue looking for better alternatives.
>>> 
>>> I would prefer to have a *single* keyword which meant both public and
>>> overridable. That would minimize the impact of this feature—instead of
>>> writing:
>>> 
>>>        public class MyViewController: UIViewController {
>>>                public func displayMe(_ me: person) { … }
>>>        }
>>> 
>>> You'd write (strawman keyword):
>>> 
>>>        openseason class MyViewController: UIViewController {
>>>                openseason func displayMe(_ me: person) { … }
>>>        }
>>> 
>>> And then `MyViewController` could be subclassed, and `displayMe`
>>> overridden.
>>> 
>>> --
>>> Brent Royal-Gordon
>>> Architechies
>>> 
>> 
>> 
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