> On Nov 3, 2017, at 5:17 AM, Mike Kluev <[email protected]> wrote:
>
> On 3 November 2017 at 03:05, Adam Kemp <[email protected]
> <mailto:[email protected]>> wrote:
>
>
> Would it be an error to have an entry in the “ledger” but not a corresponding
> implementation?
>
> definitely so. and vice versa.
>
> Mike
>
If that’s the case then this wouldn’t solve one of the major use cases I listed
for this: splitting up cross-platform classes into platform-specific files. The
idea is that each target contains a different subset of the files. Consider a
case where two platforms are similar enough to share some code but not all
code. For instance:
Class.swift
Class.UIKit.swift // Used by iOS + watchOS
Class.iOS.swift
Class.watchOS.swift
Class.macOS.swift
There are three targets, and two of the targets include Class.UIKit.swift but
not the third. So what do you put in the ledger?
For a real-world example, consider a custom view that is used for presenting
content in an app that shares code on iOS, tvOS, and macOS. Much of the logic
for this is shared, including rendering which is done using CoreGraphics. You
could write that class something like this:
PresentationView.swift:
import CoreGraphics
partial class PresentationView {
private func draw(inContext context: CGContext) {
// Shared CoreGraphics drawing
}
}
PresentationView.UIKit.swift: // Used by iOS + tvOS
import UIKit
partial class PresentationView : UIView {
func draw(_ rect: CGRect) {
self.draw(inContext: UIGraphicsGetCurrentContext())
}
}
PresentationView.AppKit.swift:
import AppKit
partial class PresentationView : NSView {
func draw(_ dirtyRect: NSRect) {
self.draw(inContext: NSGraphicsContext.currentContext()?.CGContext)
}
}
This is exactly the technique that I’ve used in the past (in C#) to share code
across iOS, Android, macOS, and WPF. It’s really powerful, but the ledger would
make it much harder._______________________________________________
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