Thuta Learning
Search
IntermediateMobile Developmentintermediate

State in SwiftUI (@State, @Binding)

Relax. We'll talk through this in plain words — no textbook voice.

What you'll walk away with

  • Understand State in SwiftUI (@State, @Binding), without any of the intimidation
  • Get hands-on running Xcode/SwiftUI code yourself
  • Apply this concept immediately in a real project

Let's think about this for a moment

Since a SwiftUI View is a struct, it's immutable — writing `var count = 0` inside a View means you can't modify that value (you'll get a compile error). Only by using `@State private var count = 0` does SwiftUI store the value 'behind the scenes' of the View, and automatically re-render the View whenever that value changes. `@Binding` is a property wrapper that 'connects' a parent's `@State` to a child View — when the child modifies the value, the parent's state updates immediately too (this is the State Hoisting pattern, similar to Compose).

Let's connect this to a real-world scenario

In a counter app, if you write `@State private var count = 0` and do `count += 1` on a button tap — the `Text("\(count)")` on screen will automatically update and the number will increase. Using `@Binding`, you can write something like `ToggleSwitch(isOn: $isEnabled)` to connect state from the parent via the `$` prefix, letting you reuse the `ToggleSwitch` View across different parents.

Let's look at it together

swift
struct Counter: View {
    @State private var count = 0

    var body: some View {
        VStack {
            Text("Count: \(count)")
                .font(.title)
            Button("Increment") {
                count += 1
            }
        }
    }
}
You should see
Tapping the button should show 'Count: 0' → 'Count: 1' → 'Count: 2', updating live on screen.

Try it in 5 minutes

Run the `Counter` View and tap the button 5 times — confirm the count value updates live. Then try deleting `@State` and see what compile error you get.

A quick word of caution

Use `@State` only for a View's 'local, private' state — for app-wide state (like login status), you should use `ObservableObject` (covered in the Advanced chapter) instead of `@State`.

Easy traps

  • Trying to modify a View property without `@State` — you'll get a compile error ('Cannot assign to property')
  • Trying to expose `@State` as a public/external property — `@State` should be private; use `@Binding` if you need to share it with the parent

Now try it yourself

Run the `Counter` View and tap the button 5 times — confirm the count value updates live. Then try deleting `@State` and see what compile error you get.

You'll know it worked when: Tapping the button should show 'Count: 0' → 'Count: 1' → 'Count: 2', updating live on screen.

State in SwiftUI (@State, @Binding) | Thuta Learning