[swift-evolution] [proposal] Allow "let" for computed properties which only reference immutable data

[Leonardo Pessoa]

David, I'm thinking about the side effects calling a computed property has
and although I see some use cases for let properties I also see
workarounds. For example, a lazy initialiser will solve the issue of
running a certain code only once and caching its value. I also start to
think that any case in this proposal will be solved by lazy initialisers
thus rendering it unnecessary.


On 17 May 2016 at 17:50, David Sweeris <davesweeris at mac.com> wrote:

> You can't, if you're extending a pre-existing type.
>
> I'd think that it might be possible to do some caching if the compiler
> knows that a computed property is constant, but maybe it doesn't work that
> way.
>
> - Dave Sweeris
>
> On May 17, 2016, at 14:40, Leonardo Pessoa via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> If the value of the property is a constant, shouldn't you just declare it
> as one? If you have any sort of computation in it, even concatenating two
> constant strings, can you really say this is a constant? And you would also
> be overloading the compiler into trying to check for every property you use
> let if the overall computation is constant or not. IMO, let isn't really
> the most appropriate keyword to use for properties.
>
> - Leonardo
>
> On 13 May 2016 at 04:44, Andru Felipe Zuniga via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> It would be useful for clarification of a computed property being
>> constant in extensions. For example:
>>
>> extension SKSpriteNode {
>>         static let type: String {
>>                 return “Sprite”
>>         }
>> }
>>
>> Andru
>>
>>
>>
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