[swift-evolution] [swift-evolution-announce] [Review] SE-0023 API Design Guidelines

[Dave Abrahams]

on Sun Jan 24 2016, David Owens II <david-AT-owensd.io> wrote:

> Sorry, I meant to add the do() version too in order to show the
> difference better. /sigh

do() version?

>
>> On Jan 24, 2016, at 4:53 PM, David Owens II via swift-evolution
>> <swift-evolution at swift.org> wrote:
>> 
>> 
>>>> I guess my point is this: codifying a convention seems pre-mature as
>>>> that convention doesn't bring the safety goals of the language into a
>>>> place that's verifiable. All of the other guidelines are simply about
>>>> clarity of use, this convention has a far reaching impact.
>>> 
>>> Sorry, could you clarify what you mean by "bring the safety goals of the
>>> language into a place that's verifiable" and clarify why having a "far
>>> reaching impact" would somehow conflict with being "about clarity of use?"
>>> 
>>> It seems to me that this convention is about how to express whether a
>>> method is going to mutate so it's clear at the use-site.  What am I
>>> missing?
>> 
>> 
>> The problem is it's unclear to me whether you mean mutate in the
>> true sense of the word or only applied to a struct with a function
>> annotated with the mutating keyword.
>> 
>> The naming convention provides no safety when dealing with
>> non-struct types as we cannot enforce that a method on a class does
>> not mutate it's internal members.
>> 
>> That's the clarity I'm looking for.
>> 
>> Given this API set:
>> 
>> protocol InPlaceable {
>>     mutating func doInPlace()
>> }
>> 
>> public struct Foo: InPlaceable {
>>     mutating func doInPlace() {}
>> }
>> 
>> public class Bar: InPlaceable {
>>     func doInPlace() {}
>> }
>> 
>> var lie: InPlaceable = Bar()
>> lie.doInPlace()
>> 
>> let lie2 = Bar()
>> lie2.doInPlace()
>> 
>> The convention will tell us a lie unless we are extremely
>> careful. It's this lie that concerns me. We cannot guarantee that
>> the "doInPlace" truly matches the definition we are seeking.
>> 
>> 
>> -David
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>

-- 
-Dave