UnconstrainedEnvironmentObject.swift

import SwiftUI

extension EnvironmentValues {
  struct UnconstrainedObjectKey<Object>:
    EnvironmentKey
    where
    Object: AnyObject
  {
    static var defaultValue: Object? {
      nil
    }
  }

  subscript <Object>() -> Object? where Object: AnyObject {
    get {
      self[UnconstrainedObjectKey<Object>.self]
    }
    set {
      self[UnconstrainedObjectKey<Object>.self] = newValue
    }
  }
}

@propertyWrapper
public struct UnconstrainedEnvironmentObject<ObjectType>:
  DynamicProperty
  where
  ObjectType: ObservableObject
{
  @Environment(\.[])
  var _object: ObjectType?

  @dynamicMemberLookup
  public struct Wrapper {
    let object: ObjectType

    public subscript <Subject>(
      dynamicMember keyPath: ReferenceWritableKeyPath<ObjectType, Subject>
    ) -> Binding<Subject> {
      Binding(
        get: {
          object[keyPath: keyPath]
        },
        set: { newValue in
          object[keyPath: keyPath] = newValue
        }
      )
    }
  }

  public var wrappedValue: ObjectType {
    guard let object = _object else {
      fatalError("Object of type '\(ObjectType.self)' not found")
    }
    return object
  }

  public var projectedValue: Wrapper {
    Wrapper(object: wrappedValue)
  }

  public init() {}
}

extension View {
  public func unconstrainedEnvironmentObject<T>(
    _ object: T
  ) -> some View where T: ObservableObject {
    environment(\.[], object)
  }
}