@State property wrapper in iOS Swift

Introduction

The @State property wrapper lets your app remember and update values that can change over time. It helps your app update the screen automatically when data changes.

When you want to keep track of a button tap count and show it on the screen.

When you need to update a text field as the user types.

When you want to toggle a switch and change the UI based on its state.

When you want to show or hide parts of the screen based on user actions.

Syntax

iOS Swift

@State private var variableName: Type = initialValue

Use @State only inside SwiftUI views to hold simple, local data.

Mark the variable as private to keep it safe inside the view.

Examples

A boolean state to track if a switch is on or off.

iOS Swift

@State private var isOn: Bool = false

An integer state to count button taps.

iOS Swift

@State private var count: Int = 0

A string state to hold user input text.

iOS Swift

@State private var username: String = ""

Sample App

This app shows a button and a text label. Each time you tap the button, the number increases and the text updates automatically. This happens because count is marked with @State, so SwiftUI knows to refresh the screen when it changes.

iOS Swift

import SwiftUI

struct ContentView: View {
  @State private var count: Int = 0

  var body: some View {
    VStack(spacing: 20) {
      Text("Button tapped: \(count) times")
        .font(.title)
      Button("Tap me") {
        count += 1
      }
      .padding()
      .background(Color.blue)
      .foregroundColor(.white)
      .cornerRadius(8)
    }
    .padding()
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}

Important Notes

Only use @State for simple, local data inside one view.

For sharing data between views, use other tools like @ObservedObject or @EnvironmentObject.

Changing a @State variable automatically refreshes the view to show the new data.

Summary

@State keeps track of changing data inside a SwiftUI view.

It automatically updates the screen when the data changes.

Use it for simple, local variables like counters, toggles, or text inputs.