Re: Swift: should computed properties be able to throw exceptions?
Re: Swift: should computed properties be able to throw exceptions?
- Subject: Re: Swift: should computed properties be able to throw exceptions?
- From: Rick Mann <email@hidden>
- Date: Fri, 21 Aug 2015 20:18:49 -0700
> On Aug 21, 2015, at 20:06 , Greg Parker <email@hidden> wrote:
>
>
>> On Aug 21, 2015, at 6:15 PM, Rick Mann <email@hidden> wrote:
>>
>>> On Aug 21, 2015, at 18:13 , Quincey Morris <email@hidden> wrote:
>>>
>>> I’d recommend you try to avoid calling the Swift side “exceptions”. It’s error handling, and although it’s not completely unlike exception handling in other (non-Obj-C) languages, it’s treacherous to confuse the two when dealing with Obj-C.
>>
>> Really? It sure seems to be precisely an exception, in that it's an exception to the "normal" flow of control (e.g. return). Just because the type of what's thrown is called "Error" doesn't change the fact that they're conceptually exceptions (as opposed to, say, returning a boolean true/false to indicate an error).
>
> We avoid the word "exception" for Swift's error handling.
>
> The fundamental feature of exception systems is that the call site need not do anything. If the call site does nothing, the exception automatically unwinds past it. There is no syntactic difference between a call site that may throw and a call site that will never throw.
>
> Swift's error handling is different: the possibility of error is explicit at the call site. Some people think this is better (no invisible execution paths) and some people think it is worse (too noisy). Either way the model is different enough that we don't call it exception handling.
>
> The fact that Swift's errors map to Objective-C NSError instead of Objective-C exceptions is another reason to avoid "exception".
Okay, so an Objective-C method that throws an exception...what happens?
Also, if the method of the call site is marked as "throws," does that mean the error will propagate out?
Pity it's not a real exception mechanism.
--
Rick Mann
email@hidden
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