Create a typed array w/ N items in it using Swift

Question

I have a method that I'm using to create an array w/ n of a specific type of object in it:

func many(count: Int) -> [Cube] {
  var cubes: [Cube] = []
  for i in 0...count {
    let cube = CubeFactory.single()
    cubes.append(cube)
  }
  return cubes
}

This works but I'm sure there's a more swift like way to do this. Any one know how this can be refactored?

func many(count: Int) -> [Cube] { return [Cube](count: count, repeatedValue: Cube.single()) } — Mick MacCallum
– Mick MacCallum, Commented Jan 29, 2015 at 23:27
This is marked as a duplicate, but the referenced question refers to initializing an array with identical values, this question is about initializing it with different values. — David Berry
– David Berry, Commented Jan 29, 2015 at 23:27
Although at some point it changed so that it probably is initializing it with a single value now. Need some clarification from the OP about which is actually desired. — David Berry
– David Berry, Commented Jan 29, 2015 at 23:29
Sorry I didn't clarify but they need to be different objects, just of the same type. — Kyle Decot
– Kyle Decot, Commented Jan 29, 2015 at 23:45

Airspeed Velocity · Accepted Answer · 2015-01-30 00:02:34Z

3

Does CubeFactory.single() actually do anything other than return the same instance every time?

If it does active stuff, return map(0..<count) { _ in CubeFactory.single() } (or numerous variants) will give you an array of them.

(the _ in really oughtn’t to be necessary, but Swift’s type inference gets a bit flummoxed without it and you’ll get an error about half-open intervals – the other possibility for the overloaded ..< operator – not conforming to SequenceType)

If it’s just inert and every cube is identical, return Array(count: count, repeatedValue: Cube.single()) is all you need.

edited Jan 30, 2015 at 0:02

answered Jan 29, 2015 at 23:33

Airspeed Velocity

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2 Comments

Kyle Decot Over a year ago

Thanks for the information! Do you happen to know if the _ in thing is going to be addressed at some point?

Airspeed Velocity Over a year ago

no idea but you’ve reminded me I haven’t filed a radar for it :-)

jrc · Accepted Answer · 2015-09-15 20:11:21Z

2

In Swift 2, this is

let array = (0..<30).map { _ in CubeFactory.single() }

answered Sep 15, 2015 at 20:11

jrc

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Comments

David Berry · Accepted Answer · 2015-01-29 23:40:32Z

0

Not sure if it's exactly what you're looking for, but you can use:

let array = map(0..<30) { _ in CubeFactory.single() }

edited Jan 29, 2015 at 23:40

answered Jan 29, 2015 at 23:26

David Berry

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2 Comments

Airspeed Velocity Over a year ago

You shouldn’t need that SequenceOf – ranges are already sequences.

David Berry Over a year ago

That's what I thought too, but it didn't seem to work that way. Trying it again it does, so I've updated it.

Peter Kreinz · Accepted Answer · 2018-11-08 12:02:57Z

0

Swift 4.2

struct Cube {
    let id:Int
}

...    

let array = (0..<24).compactMap {
    return Cube(id: $0)
}

answered Nov 8, 2018 at 12:02

Peter Kreinz

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1 Comment

Womble Over a year ago

Out of curiosity, why the use of compactMap over map, in this example?

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