Create an environment key

struct SensitiveKey: EnvironmentKey {
  static let defaultValue: Bool = false
}

Introduce new value to `Environment`

Once we declare a data type and a key to access it, we introduce this newly create key/value to EnvironmentValues using extension.

extension EnvironmentValues {
  var isSensitive: Bool {
    get { self[SensitiveKey.self] }
    set { self[SensitiveKey.self] = newValue }
  }
}

Using

struct PasswordField: View {
  let password: String

  // we read environment value with `@Environment`
  @Environment(\.isSensitive) private var isSensitive

  var body: some View {
    VStack {
        // View then react to `isSensitive` value by redact the password if `isSensitive` is `true`.
        Text(password).redacted(reason: isSensitive ? .placeholder: [])
    }
  }
}

To use this PasswordField

struct ContentView: View {
  // we create a @State to control `isSensitive` env value
  @State private var isSensitive = false

   var body: some View {
       VStack {
         // bind the state var to a toggle
         Toggle("Sensitive", isOne: $isSensitive)

         // use the state var to override `isSensitive` env value of `PasswordField`
         PasswordField(password: "123456").isSensitive(isSensitive)
       }
   }
}

Conclusion

It might not be obvious that we can create a custom environment value, but we can do that. The steps to create one are not as straightforward as we usually do, but it isn't hard if you know how to do it.

Here is a summary of how to create a new environment value.

// Create an environment key
private struct NewKey: EnvironmentKey {
    static let defaultValue: DataTypeForNewValue = defaultValue
}

// Introduce new value to EnvironmentValues
extension EnvironmentValues {
    var newEnvironmentName: DataTypeForNewValue {
        get { self[NewKey.self] }
        set { self[NewKey.self] = newValue }
    }
}

// Add a dedicated modifier (Optional)
extension View {
    func newModifier(_ value: DataTypeForNewValue) -> some View {
        environment(\.newEnvironmentName, value)
    }
}

System predefined @Environment https://developer.apple.com/documentation/swiftui/environmentvalues

https://sarunw.com/posts/how-to-define-custom-environment-values-in-swiftui/

vinhnx / notes

SwiftUI @Environment #449

Create an environment key

Introduce new value to `Environment`

Using

Conclusion