SwiftUI EnvironmentObject for Keyboard Changes

KeyboardObserver.swift

import SwiftUI
import Combine
#if os(iOS)
import UIKit.UIResponder
#endif

class KeyboardObserver: ObservableObject {
  struct State: Equatable {
    let frame: CGRect
    let isLocal: Bool // on multitasking iPad apps, all visible apps notified
  }
  @Published var state = State(frame: .zero, isLocal: true)

  #if os(iOS)
  private let didShowPublisher = NotificationCenter.default.publisher(for: UIResponder.keyboardDidShowNotification)
  private let didHidePublisher = NotificationCenter.default.publisher(for: UIResponder.keyboardDidHideNotification)
  private let didChangeFramePublisher = NotificationCenter.default.publisher(for: UIResponder.keyboardDidChangeFrameNotification)

  private var cancellables: Set<AnyCancellable> = []
  #endif

  init() {
    #if os(iOS)
    didShowPublisher
      .merge(with: didChangeFramePublisher)
      .receive(on: RunLoop.main)
      .tryMap { notification -> State in
        guard let frame = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect,
              let isLocal = notification.userInfo?[UIResponder.keyboardIsLocalUserInfoKey] as? Bool else {
          throw CocoaError(.keyValueValidation)
        }
        return State(frame: frame, isLocal: isLocal)
      }
      .replaceError(with: State(frame: .zero, isLocal: true))
      .removeDuplicates()
      .setFailureType(to: Never.self)
      .assign(to: \.state, on: self)
      .store(in: &cancellables)

    didHidePublisher
      .ignoreOutput()
      .receive(on: RunLoop.main)
      .sink { _ in
        self.state = State(frame: .zero, isLocal: true)
      }
      .store(in: &cancellables)
    #endif
  }
}