How can I define a function/closure which returns a Binding?

Question

I want make a function which make my typing easier when I must initialize a Binding in some cases!

Here is the code:

func bindingFunction(value: inout CGFloat) -> Binding<CGFloat> {
    return Binding(get: { return value }, set: { newValue in value = newValue })
}

I am getting 2 errors from xCode:

1. Parameter 'value' is declared 'inout'

Escaping closure captures 'inout' parameter 'value'

My Goal is to solve those errors in first place and finally I want make my function be generic as well, as you see my function works for Binding CGFloat which I want make it generic and then I could use it when I need Binding Bool as well.

Answer 1

As you've seen in your comments, there's not a good general solution for this. You can really only make it easier if you have a ReferenceWritableKeyPath to work with (which means no value types, such as your CGFloat).

Generally, nobody needs this, because we're all using ObservableObjects + @Published instead.

final class Model {
  var leaves = ""
}

let model = Model()
let fallenLeaves = ""
@Binding(model, keyPath: \.leaves) var leaves;
leaves = fallenLeaves
XCTAssertEqual(model.leaves, fallenLeaves)

public extension Binding {
  init(
    accessors: (
      get: () -> Value,
      set: (Value) -> Void
    )
  ) {
    self.init(get: accessors.get, set: accessors.set)
  }

  init<Root>(
    _ root: Root,
    keyPath: ReferenceWritableKeyPath<Root, Value>
  ) {
    self.init(accessors: keyPath.accessors(root))
  }
}

public extension ReferenceWritableKeyPath {
  /// Partially-applied `get` and `set` accessors for this key path.
  ///
  /// Typical usage: `accessors(root)`
  var accessors: (Root) -> (
    get: () -> Value,
    set: (Value) -> Void
  ) {
    { root in
      ( get: { root[keyPath: self] },
        set: { root[keyPath: self] = $0 }
      )
    }
  }
}