variable size array

Question

Hello,

How can I access variable size arrays in Swift 1.2?

For example

var layout:AudioChannelLayout = ...

for var i:UInt32 = 0; i < layout.mNumberChannelDescriptions; i++

{

if layout.mChannelDescriptions[i].mChannelLabel == kAudioChannelLabel_Left { /*some action*/ } // 'AudioChannelDescription' does not have a member named 'subscript'

}

Type of layout.mChannelDescriptions is (AudioChannelDescription)

TIA,

Jan E.

BTW it would be nice if the Analyzer's remarks could be copied

Swift

6.0k

Posted by

jeschot

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Answer 1

That worked!

Neat-o!

One thing to note here is that an

UnsafeMutableBufferPointer

is actually a

Collection

, so you can use

Collection

methods on it. For example, you can use

map(_:)

to map from the elements to a

String

and then

joined(separator:)

to join those strings together, like so:

channelLayoutDescriptionString = withUnsafeMutablePointer(to: &channelLayout.mChannelDescriptions) { start in
    let channelDescriptions = UnsafeMutableBufferPointer(start: start, count: Int(channelLayout.mNumberChannelDescriptions))
    return channelDescriptions.map { desc in
        desc.mChannelLabel.audioChannelLabelString
    }.joined(separator: ", ")
}

Much nicer (IMO, obviously) than messing around with a bunch of mutable state (-:

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Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Posted by

eskimo

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Answer 2

Hi there! I'm back with a related question.

Say I want to create an AudioChannelLayout in Swift from scratch - how would I go about creating a variable sized array in Swift that I can assign to mChannelDescriptions?

For example, say I have a Swift Array of AudioChannelDescriptions and I want to make that a C tuple variable sized array to set the the AudioChannelLayout's mChannelDescriptions with.

Posted by

gregvideovillage

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variable size array

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