BindingUnwrapperView

BindingUnwrapperView.md

BindingUnwrapperView

⚠️ WARNING ⚠️

This concept still not working and I don't have a clue (so far) why it do not compile because the only error I get is:

failed to produce diagnostic for expression; please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the project

BindingUnwrapperView is a view that safely turns a Binding<Value?> into a Binding<Value> and when it fails, provides a fallback block that can be used to return some View.

Use case

Some views can have Binding<Value> fields (for example @Binding var Todo), where the Value can be a struct that has optional fields. Maybe, the field is desirable to be a bind of some other component, for example a TextField where text should be a Binding<String>.

BindingUnwrapperView enable to safely bind optional fields of a struct in case the value is not nil, so the TextField or any other View that expects a non optional Value, can be conditioned to rendered.

For a more concrete example, see next the topic below.

Usage

struct Todo {
  var text: String
  var checked: Bool = false
  var due: Date?              // notice due is optional
}

struct TodoView: View {
  @Binding var todo: Todo // This todo will not by optional but todo.due is
  
  var body: some View {
    VStack {
      HStack {
        TextField("text", text: $todo.text)
        Button {
          withAnimation {
            todo.checked.toggle()
          }
        } label: {
          if todo.checked {
            Image(systemName: "checkmark.square")
          } else {
            Image(systemName: "square")
          }
        }
      }
      BindingUnwrapperView($todo.due) { $due in // BindingUnwrapper view proviedes a Binding<Date> instead of Binding<Date?>...
        DatePicker("Due", selection: $due) // ...So it can be safely bindinde with DataPicker's selection prop...
      } fallback: { // ...otherwise, render something else.
        Text("")
          .font(.caption)
          .foregroundColor(.gray)
      }
    }
  }
}

License

MIT

BindingUnwrapperView.swift

/*
  BindingUnwrapperView.swift
  
  MIT License
  Copyright (c) 2022 Jan Cassio
  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,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/

import SwiftUI

struct BindingUnwrapperView<Content, Value>: View where Content: View {
  @Binding var value: Value?
  
  let content: (Binding<Value>) -> Content
  let fallback: () -> Content
  
  private var resolved: Binding<Value>? {
    guard let value else {
      return nil
    }
    
    return Binding(
      get: { value },
      set: { newValue in self.value = newValue }
    )
  }
  
  init(
    _ value: Binding<Value?>, 
    @ViewBuilder content: @escaping (Binding<Value>) -> Content, 
    @ViewBuilder fallback: @escaping () -> Content
  ) {
    self._value = value
    self.content = content
    self.fallback = fallback
  }
  
  var body: some View {
    if let resolved {
      content(resolved)
    } else {
      fallback()
    }
  }
}