[swift-evolution] [Review] SE-0070: Make Optional Requirements Objective-C only

[Charles Srstka]

Why would you want lack of an optional method to be a fatal error, either?

Charles

> On Apr 27, 2016, at 5:29 PM, Andrew Bennett <cacoyi at gmail.com> wrote:
> 
> Hi Charles,
> 
> My initial idea just had a fatalError, without a throw. It's better IMO, but less Swift-y. It's not obvious from the Swift protocol definition that this could happen. I'm not sure if it's possible for the extension method to have @noreturn or similar on it.
> 
> On Thursday, 28 April 2016, Charles Srstka <cocoadev at charlessoft.com <mailto:cocoadev at charlessoft.com>> wrote:
>> On Apr 27, 2016, at 9:30 AM, Andrew Bennett via swift-evolution <swift-evolution at swift.org <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>> 
>> Sorry if this has been discussed, but have you considered dropping optional entirely, making it throw, and a default implementation that throws a selector not found exception?
>> 
>> This is approximately what you would expect using it in objc. I don't think it has the complexity discussed in the proposals alternatives for other call site issues.
>> 
>> If it throws you can call with "try?" to get similar functionality in most cases.
>> 
>> This assumes that respondsToSelector doesn't pick up the Swift default implementation.
> 
> Is there any case where you’d actually want to display a runtime error as a result of a delegate not implementing an optional method, though? Even setting aside that the method’s supposed to be optional, leaving out a needed delegate method seems more like a programmer error than a runtime error.
> 
> Charles
> 

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