[swift-evolution] Pitch: Support for map and flatMap with smart key paths

[Saagar Jha]

It reads better and feels more natural. In my mind, it’s similar to the difference between 

["1", "2", "3"].flatMap { Double($0) }

and

["1", "2", "3"].flatMap(Double.init)

Saagar Jha

> On Jun 9, 2017, at 16:06, Max Moiseev via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Sorry. I might be missing something. Why is this better than:
> 
> let allEmployees = Set(managers.flatMap { $0.directReports }
> 
> ?
> 
>> On Jun 7, 2017, at 10:35 AM, Adam Sharp via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> The new smart key path feature is really lovely, and feels like a great addition to Swift.
>> 
>> It seems like it might be straightforward to add overloads of `map` and `flatMap` to the standard library to make use of the new functionality:
>> 
>> 	let managers = flatOrganisation.managers
>> 	let allEmployees = Set(managers.flatMap(\.directReports))
>> 	let employeeNames = Set(allEmployees.map(\.name))
>> 
>> This feels like a really natural way of working with key paths in a functional style. It makes a lot of sense for collections, and possibly for Optional too (although as far as I can see optional chaining is more or less equivalent, and with more compact syntax).
>> 
>> I’m hoping that this might be low-hanging fruit that could be considered for the Swift 4 release. I’d be happy to have a go at writing a proposal if there’s interest!
>> 
>> –Adam
>> 
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