---
title: "onChange(of:initial:_:)"
framework: swiftui
role: symbol
role_heading: Instance Method
path: "swiftui/view/onchange(of:initial:_:)-4psgg"
---

# onChange(of:initial:_:)

Adds a modifier for this view that fires an action when a specific value changes.

## Declaration

```swift
nonisolated func onChange<V>(of value: V, initial: Bool = false, _ action: @escaping (V, V) -> Void) -> some View where V : Equatable

```

## Parameters

- `value`: The value to check against when determining whether to run the closure.
- `initial`: Whether the action should be run when this view initially appears.
- `action`: A closure to run when the value changes.

## Return Value

Return Value A view that fires an action when the specified value changes.

## Discussion

Discussion You can use onChange to trigger a side effect as the result of a value changing, such as an Environment key or a Binding. The system may call the action closure on the main actor, so avoid long-running tasks in the closure. If you need to perform such tasks, detach an asynchronous background task. When the value changes, the new version of the closure will be called, so any captured values will have their values from the time that the observed value has its new value. The old and new observed values are passed into the closure. In the following code example, PlayerView passes both the old and new values to the model. struct PlayerView: View {     var episode: Episode     @State private var playState: PlayState = .paused

var body: some View {         VStack {             Text(episode.title)             Text(episode.showTitle)             PlayButton(playState: $playState)         }         .onChange(of: playState) { oldState, newState in             model.playStateDidChange(from: oldState, to: newState)         }     } }