[swift-users] Best way to solve ambiguous references to methods

[Harlan Haskins]

A quick-and-dirty way would be to explicitly cast to the protocol type before calling the function.

let flatArray = (mapArray as SequenceType).flatten()

Or in this case you could just mapArray.flatMap()

> On Dec 5, 2015, at 12:38 PM, Vinicius Vendramini <vinivendra at gmail.com> wrote:
> 
> So I was playing around with Sequences, and I came across a problem I haven't been able to solve in a decent way. I’ve reduced it to a simpler example here:
> 
> 
> let array : [Int] = [1, 2, 3]
> 
> let mapArray = array.map { $0 }
> 
> let flatArray = mapArray.flatten() // Error!
> 
> 
> This last line of code prints the following error:
> 
> 
> let flatArray = mapArray.flatten() // Error!
>                 ^~~~~~~~
> Swift.SequenceType:4:17: note: found this candidate
>     public func flatten() -> FlattenSequence<Self>
>                 ^
> Swift.CollectionType:4:17: note: found this candidate
>     public func flatten() -> FlattenCollection<Self>
>                 ^
> Swift.CollectionType:4:17: note: found this candidate
>     public func flatten() -> FlattenBidirectionalCollection<Self>
>                 ^
> 
> 
> As far as I understand it, the error happens because several protocols extensions implement the `flatten` method, and `mapArray` (which is of type `Array<Optional<Int>>`) conforms to a few of those, which means the compiler has no way of knowing which one I intend on using.
> 
> How do I solve this?
> 
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