Hey Hooman, that’s very elegant. I didn’t think of it like that and will
definitely use, thx!
Though wouldn’t “defer init()” take it a step further: 1) reduce redundant
boilerplate 2) prevent forgetting/bugs and 3) smaller memory allocation
footprint? It also fits well with the existing Swift 2 “defer” keyword used in
functions. Here’s what your sample would look like:
import UIKit
import AVFoundation
class SomeViewController: UIViewController {
// MARK: Properties
private var videoPlayer: AVPlayer
private var videoPlayerLayer: AVPlayerLayer
// MARK: - Object Lifecycle
override init(nibName: String?, bundle nibBundle: NSBundle?) {
super.init(nibName: nibName, bundle: nibBundle)
}
required init?(coder decoder: NSCoder) {
super.init(coder: decoder)
}
defer init() {
videoPlayer = AVPlayer(URL: NSURL(fileReferenceLiteral: "movie.mov"))
videoPlayerLayer = AVPlayerLayer(player: player)
}
}
> On Apr 30, 2016, at 2:18 PM, Hooman Mehr via swift-evolution
> <[email protected]> wrote:
>
> Besides the ages old designated initializer pattern that is already suggested
> (having a few designated initializers and a bunch of convenience
> initializers), this is how I have been dealing with this since Swift 1.0:
>
> import UIKit
> import AVFoundation
>
> class SomeViewController: UIViewController {
>
> private typealias My = SomeViewController
>
> // MARK: Properties
>
> private var videoPlayer: AVPlayer
> private var videoPlayerLayer: AVPlayerLayer
>
> // MARK: - Object Lifecycle
>
> override init(nibName: String?, bundle nibBundle: NSBundle?) {
>
>
> (videoPlayer, videoPlayerLayer) = My.commonInitialization()
>
> super.init(nibName: nibName, bundle: nibBundle)
> }
>
> required init?(coder decoder: NSCoder) {
>
> (videoPlayer, videoPlayerLayer) = My.commonInitialization()
>
> super.init(coder: decoder)
> }
>
>
> private static func commonInitialization() -> (AVPlayer, AVPlayerLayer) {
>
> let player = AVPlayer(URL: NSURL(fileReferenceLiteral: "movie.mov"))
> let layer = AVPlayerLayer(player: player)
>
> return (player,layer)
> }
> }
>
> It is not perfect, but good enough for me. I usually use this when I have
> more than one designated initializer and they share a significant amount of
> code. I usually also have input parameters for this commonInitialization
> static or class method. I make it a class method when I anticipate
> subclassing of the class.
>
> Side Note: As you see, I typically define a couple of private type aliases
> (Usually `I` and/or `My`) to help with readability of code involving static
> members.
>
>> On Apr 27, 2016, at 2:52 PM, Shannon Potter via swift-evolution
>> <[email protected] <mailto:[email protected]>> wrote:
>>
>> Consider a relatively-common init pattern:
>>
>> class SomeViewController: UIViewController {
>>
>> // MARK: Properties
>>
>> private var videoPlayer: AVPlayer
>> private var videoPlayerLayer: AVPlayerLayer
>>
>> // MARK: - Object Lifecycle
>>
>> override init(nibName: String?, bundle nibBundle: NSBundle?) {
>> super.init(nibName: nibName, bundle: nibBundle)
>>
>> commonInitialization()
>> }
>>
>> required init?(coder decoder: NSCoder) {
>> super.init(coder: decoder)
>>
>> commonInitialization()
>> }
>>
>> private func commonInitialization() {
>> videoPlayer = AVPlayer(...)
>> videoPlayerLayer = AVPlayerLayer(player: videoPlayer)
>> }
>>
>> }
>>
>> This does not work. Both properties are non-optional, and the compiler
>> complains that they are not initialized in either init method. It seems
>> rather common to want a single point of contact regarding object
>> initialization, regardless of the path taken to initialize that object.
>> Ideally, objects could all be funneled to one designated initializer, but
>> this isn’t always the case.
>>
>> What are people’s thoughts about either a specialized function that is
>> always called at the very end of each object’s lifecycle OR some sort of
>> attribute for a function that hints that the compiler should follow it if
>> called in an init function to check for property initialization?
>>
>> func commonInit() {
>>
>> }
>>
>> or
>>
>> @extend_init private func commonInitialization() {
>>
>> }
>> _______________________________________________
>> swift-evolution mailing list
>> [email protected] <mailto:[email protected]>
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>
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