DSFValueBinders

ValueBinder

A ValueBinder creates a two-way binding object to allow sharing of a value between objects.

This is mildly similar to @Binding in SwiftUI but doesn’t rely on SwiftUI – meaning it can be used pretty much anywhere Swift can.

Creating

You can define a binder using the standard initializer.

This initializer also allows you to supply a callback block that gets triggered when the wrappedValue changes.

let countBinder = ValueBinder<Int>(0) { newValue in
   Swift.print("countBinder changed: \(newValue)")
}
...
countBinder.wrappedValue = 4  // triggers the update callback

Registering for change updates

You can hand your ValueBinding object to another class which can supply a block to be called when the ValueBinder wrapped value changes.

class AnotherClass {
   init(_ binder: ValueBinder<Int>) {
      binder.register(self) { newValue in
         Swift.print("Binding detected change: \(newValue)")
      }
   }
}

Additionally, if you hold on to the binder object your class can update the ValueBinder value too!

class AnotherClass {
   let countBinder: ValueBinder<Int> 
   init(_ binder: ValueBinder<Int>) {
      countBinder = binder
      countBinder.register(self) { newValue in
         Swift.print("Binding detected change: \(newValue)")
      }
   }
   
   func userPressed() {
      countBinder.wrappedValue += 1
   }
}

‘Registered’ listeners are bound weakly to the ValueBinder, meaning that a listener

Updating the ValueBinder value

Any object that holds a ValueBinder object can update the wrapped value.

_countBinder.wrappedValue += 1

All objects that have registered for change callbacks will be notified of the change in value.

KeyPathBinder

A KeyPathBinder is a specialization of the ValueBinder that can track a dynamic keypath

// The dynamic property to bind to. This might be (for example) bound to a control from interface builder.
@objc dynamic var state: NSControl.State = .on

// Our binding object
lazy var boundKeyPath: KeyPathBinder<MyViewController, NSControl.StateValue> = {
   return try! .init(self, keyPath: \.buttonState) { newValue in
      Swift.print("boundKeyPath notifies change: \(String(describing: newValue))")
   }
}()

Combine

Both binder types expose a property passthroughSubject which you can hook up to your combine workflow.

let binder = ValueBinder(0) 
...
let cancellable = binder.passthroughSubject.sink { newValue in
   // do something with `newValue`
}

License

MIT License

Copyright (c) 2022 Darren Ford

Permission is hereby granted, free of charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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GitHub

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