[swift-evolution] Idea: Allow/require "let" in property setter name declarations

[Geordie J]

Comments below

> Am 06.05.2016 um 13:48 schrieb Haravikk via swift-evolution <swift-evolution at swift.org>:
> 
> Actually a setter has more in common with a function, in which case the let implicit, the difference is that a setters type is also implicit. In fact, you don’t even need to specify a name in a setter at all, as the default is newValue and you can just use that.
> 
> I’m more curious whether we even need a named new value at all, or if setters should just look like the following instead:
> 
> 	set { sideLength = $0 / 4.0 }

This is great!
Why not have the opportunity to name the variable like in closures, but have it default to $0:

class Square {
  var sideLength: Double = 0.0
  var perimeter: Double {
    set { newPerimeter in
      sideLength = newPerimeter / 4.0
    }
  }
}

> 
> As this would be more consistent with anonymous closure arguments, rather than using newValue which is arbitrary. I’ve never encountered an occasion where I’ve needed a custom name, and I only use external vs internal names on functions where I can make an external name that flows better, but perhaps doesn’t mesh with my other internal variable names.
> 
>> On 6 May 2016, at 12:09, Ian Partridge via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Currently, the syntax for explicitly naming property setters is:
>> 
>> class Square {
>>   var sideLength: Double = 0.0
>> 
>>   var perimeter: Double {
>>     get {
>>       return sideLength * 4.0
>>     }
>>     set(newPerimeter) { // declares newPerimeter parameter, "let" not allowed
>>       sideLength = newPerimeter / 4.0
>>     }
>>   }
>> }
>> 
>> Compare this with how extraction of associated values from enumerations looks:
>> 
>> enum ServerResponse {
>>   case Failure(String)
>>   case Result(Int)
>> }
>> let response = ServerResponse.Result(404)
>> 
>> switch response {
>> case .Failure(let reason): // let is required here
>>   print(reason)
>> case .Result(let code):
>>   print(code)
>> }
>> 
>> For consistency, would it be better to allow/require:
>> 
>> class Square {
>>   var sideLength: Double = 0.0
>> 
>>   var perimeter: Double {
>>     get {
>>       return sideLength * 4.0
>>     }
>>     set(let newPerimeter) {  // declares newPerimeter parameter
>>         sideLength = newPerimeter / 4.0
>>     }
>>   }
>> }
>> 
>> The idea would apply to didSet{} and willSet{} too.
>> 
>> --
>> Ian Partridge
>> 
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>> https://lists.swift.org/mailman/listinfo/swift-evolution
> 
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160508/05a10429/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 455 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160508/05a10429/attachment.sig>