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arraysswift
chris P
chris P

Reputation: 6599

Swift Error: Cannot convert value of type 'ArraySlice' to expected argument type

I'm getting this error and am new to Swift. I want to take the last 5 points of an array >= 5, and pass those 5 points as an array argument to a function. How can I achieve this and get past this error?

Cannot convert value of type 'ArraySlice' to expected argument type '[CGPoint]'

if (self.points?.count >= 5) {
    let lastFivePoints = self.points![(self.points!.count-5)..<self.points!.count]
    let angle = VectorCalculator.angleWithArrayOfPoints(lastFivePoints)
}

Upvotes: 46

Views: 27811

Answers (3)

Ted
Ted

Reputation: 23756

I tried using Array(lastFivePoints) but i got error

Type of expression is ambiguous without more context

enter image description here

I ended up doing:

let arr = lastFivePoints.map({ (x) -> T in
                            return x
                        })

where T is the content class CGPoint for this example

Upvotes: 2

Ohmy
Ohmy

Reputation: 2221

Instead of the range operator you can use prefix(upTo end: Self.Index) method that return ArraySlice which makes your code shorter. Method's definition: The method returns a subsequence from the start of the collection up to, but not including, the specified position (index). 

if (self.points?.count >= 5) {
  let lastFivePoints = Array<CGPoint>(self.points?.prefix(upTo:5)) as [AnyObject]
  let angle = VectorCalculator.angleWithArrayOfPoints(lastFivePoints)
}

// You can also do this 

let lastFivePoints = Array<CGPoint>(self.points?[0...4])

Upvotes: 4

deoKasuhal
deoKasuhal

Reputation: 2897

You need to convert ArraySlice to Array using method Array(Slice<Type>)

if (self.points?.count >= 5) {
    let lastFivePoints = Array(self.points![(self.points!.count-5)..<self.points!.count])
    let angle = VectorCalculator.angleWithArrayOfPoints(lastFivePoints)
}

Upvotes: 52

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