[swift-evolution] Smart KeyPaths

[Ricardo Parada]

Agree.

Another question.  If `Bag` does have a static thing called `myStaticThingy` would you refer to it as:

Bag.Type#myStaticThingy

?


> On Mar 22, 2017, at 12:37 PM, Matthew Johnson <matthew at anandabits.com> wrote:
> 
>> 
>> On Mar 22, 2017, at 11:16 AM, Ricardo Parada <rparada at mac.com <mailto:rparada at mac.com>> wrote:
>> 
>> I see three possibilities:
>> 
>> 1) # + «space» +«path» like this:
>> 
>> let path = # Bag.things[0].name
>> bag[path] 
>> bag[# Bag.things[0].name]
>> bag[# .things[0].name]  // Root is inferred as Bag
>> bag.things[0][# Thing.name]
>> bag.things[0][# .name] // Root is inferred as Thing
>> 
>> 2) # + «path» like this::
>> 
>> let path = #Bag.things[0].name
>> bag[path] 
>> bag[#Bag.things[0].name]
>> bag[# .things[0].name]  // Root is inferred as Bag
>> bag.things[0][#Thing.name]
>> bag.things[0][#.name]  // Root is inferred as Thing
>> 
>> 3) «Root» + # + «path» like this: 
>> 
>> let path = Bag#things[0].name
>> bag[path] 
>> bag[Bag#things[0].name]
>> bag[#things[0].name]
>> bag.things[0][#name]
>> bag.things[0][Thing#name]
> 
> I prefer the third option.  I don’t think we should go with the first option.  Allowing (or requiring) a space seems likely to be confusing.  Both the first and the second still have potential to be confusing.  If `Bag` has a static property named `things` people could be confused about what `#Bag.things` refers to.  If we’re going to use a special sigil it should be positioned such that it eliminates potential for that kind of confusion.
> 
>> 
>> 
>> 
>>> On Mar 22, 2017, at 11:47 AM, Matthew Johnson <matthew at anandabits.com <mailto:matthew at anandabits.com>> wrote:
>>> 
>>> 
>>>> On Mar 22, 2017, at 10:36 AM, Vladimir.S via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>> 
>>>> On 22.03.2017 17:37, Ricardo Parada wrote:
>>>>> 
>>>>> 
>>>>>> On Mar 22, 2017, at 9:30 AM, Vladimir.S <svabox at gmail.com <mailto:svabox at gmail.com>> wrote:
>>>>>> 
>>>>>> let path = @Bag.things[0].name
>>>>>> 
>>>>>> bag at path
>>>>>> bag at .things[0].name
>>>>>> bag at Bag.things <mailto:bag at Bag.things>[0].name
>>>>>> bag.things[0]@.name
>>>>>> bag.things[0]@Thing.name
>>>>> 
>>>>> It sounds like the @ character is serving two different purposes which confused me at first.
>>>>> 
>>>>> If I understood correctly, you are using it to get the key path but also to apply the key path to the bag struct and get the corresponding value.
>>>>> 
>>>> 
>>>> Yes. And the initial proposal suggest the following syntax accordingly:
>>>> 
>>>> let path = Bag.things[0].name
>>>> bag[path]
>>>> bag[.things[0].name]
>>>> bag[Bag.things[0].name]
>>>> bag.things[0][.name]
>>>> bag.things[0][Thing.name]
>>> 
>>> # makes a lot more sense than @ as a sigil.  It follows from #selector and #keyPath.  These are the most similar language features right now where the compiler produces special values.  I think it’s also worth noticing that values produced by #selector and #keyPath are used in normal ways.  There is no magic syntax for their use, just a typed value.  If we’re going to make a change we should use # instead of `.` for accessing these special values but we should stick with subscript for use.
>>> 
>>>> _______________________________________________
>>>> swift-evolution mailing list
>>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20170322/49763e14/attachment.html>