Live Input Validation
React to typing and show validation feedback.
Live Input Validation is a free SwiftUI Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the SwiftUI Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Guiding the User
Great forms tell users about mistakes as they type, not after they submit. This is live validation, and SwiftUI makes it natural. ✅
State Drives Everything
Validation reads the same @State string the field writes to. As the value changes, you simply recompute whether it is valid.
@State private var email = ""A Computed Check
Add a computed property that returns true when the input is valid. SwiftUI re-reads it on every keystroke, so it always stays current.
var isValid: Bool {
email.contains("@")
}Showing a Hint
Use an if in the body to reveal a message only when the input is invalid. When the value becomes valid, the hint disappears on its own.
if !isValid {
Text("Enter a valid email")
}Color as Feedback
Color speaks faster than words. Tint the hint with foregroundStyle in red so the user instantly notices something needs fixing.
Text("Enter a valid email")
.foregroundStyle(.red)Checking Length
Many rules are about size. Use the count of the string to require a minimum length, like a password of at least eight characters.
var longEnough: Bool {
password.count >= 8
}Trimming Whitespace
Users add stray spaces. Trim them before checking so an entry of only spaces does not slip through as valid by mistake.
let clean = name.trimmingCharacters(
in: .whitespaces)Guarding the Button
Tie the submit Button to your check with the disabled modifier. While the input is invalid, the button simply cannot be tapped.
Button("Save") { save() }
.disabled(!isValid)Reacting to Changes
Need to run code on each edit? The onChange modifier fires whenever the value changes, perfect for logging or extra checks.
TextField("Email", text: $email)
.onChange(of: email) { check() }It All Just Updates
You never manually refresh anything. Because validation reads state, every keystroke recomputes the hints and button for free.
Kind, Clear Feedback
Live validation turns frustration into guidance. Clear hints and a smart submit button make your form feel helpful, not strict. ✨
Quick Check
How do you stop the submit button from being tapped while input is invalid?
Recap
You built live validation from a computed check, showed colored hints, trimmed input, and disabled the button until everything was valid. 🎉
Frequently asked questions
Is the “Live Input Validation” lesson free?
Yes — the full text of “Live Input Validation” is free to read here on the web, and the SwiftUI Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the SwiftUI Academy course, upgrade to CoddyKit PRO.
What will I learn in “Live Input Validation”?
React to typing and show validation feedback. You practise SwiftUI Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start SwiftUI Academy?
No prior experience is required. SwiftUI Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Live Input Validation” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this SwiftUI Academy lesson?
Yes. Every SwiftUI Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Binding a TextField to State
- Keyboard Types & Placeholders
- SecureField for Passwords
- Live Input Validation