How to Build a Language Flashcards App in SwiftUI

A Language Flashcards app lets learners drill vocabulary with smart spaced-repetition scheduling so words stick in long-term memory. It's ideal for indie developers targeting language enthusiasts, students, and travellers who want an offline-first study tool.

iOS 17+ · Xcode 16+ · SwiftUI Complexity: Intermediate Updated: 2026-05-12

Prerequisites

Xcode 16 or later installed on macOS Sequoia
Basic familiarity with SwiftUI views, state management, and Swift concurrency
An Apple Developer account (free tier is fine for Simulator; $99/yr required for App Store)

Step-by-Step Guide

1. Define the SwiftData card model

Create a @Model class that persists each flashcard's word, translation, and SRS scheduling fields to the on-device SwiftData store.

import SwiftData
import Foundation

@Model
final class Flashcard {
    var word: String
    var translation: String
    var interval: Int        // days until next review
    var easeFactor: Double   // SM-2 ease factor
    var nextReview: Date

    init(word: String, translation: String) {
        self.word = word
        self.translation = translation
        self.interval = 1
        self.easeFactor = 2.5
        self.nextReview = .now
    }
}

2. Build the flashcard flip view

Use rotation3DEffect combined with a tap gesture to animate a smooth card flip that reveals the translation on the back face.

struct CardFlipView: View {
    let card: Flashcard
    @State private var flipped = false

    var body: some View {
        ZStack {
            if flipped {
                CardFace(text: card.translation, color: .indigo)
                    .rotation3DEffect(.degrees(0), axis: (1,0,0))
            } else {
                CardFace(text: card.word, color: .blue)
                    .rotation3DEffect(.degrees(flipped ? 180 : 0), axis: (1,0,0))
            }
        }
        .animation(.spring(duration: 0.45), value: flipped)
        .onTapGesture { flipped.toggle() }
    }
}

3. Implement spaced-repetition scheduling (SRS)

Apply a simplified SM-2 algorithm after each rating to update the card's interval, ease factor, and next review date—ensuring vocabulary surfaces at the optimal moment.

func applyRating(_ rating: Int, to card: Flashcard) {
    // rating: 0 = Again, 3 = Hard, 4 = Good, 5 = Easy
    if rating < 3 {
        card.interval = 1
    } else {
        let newEase = card.easeFactor + (0.1 - (5 - Double(rating)) * 0.08)
        card.easeFactor = max(1.3, newEase)
        card.interval = max(1, Int(Double(card.interval) * card.easeFactor))
    }
    card.nextReview = Calendar.current.date(
        byAdding: .day, value: card.interval, to: .now
    ) ?? .now
}

Common Pitfalls

Forgetting to clamp ease factor: Without a minimum (1.3), cards can converge to near-zero intervals and spam the user.
Blocking the main thread with bulk imports: Insert large card sets inside a ModelActor background context to keep the UI responsive.
Losing flip state on scroll: Scope @State private var flipped inside the card view so each card tracks its own state independently.

Monetization with Subscriptions

A subscription model fits Language Flashcards perfectly: offer a free tier capped at one deck, then unlock unlimited decks, audio pronunciation, and progress analytics behind a monthly or annual StoreKit subscription. Use Product.products(for:) to fetch your subscription IDs from App Store Connect and Transaction.currentEntitlements to gate premium features—no server required, since StoreKit 2 validates receipts on-device.

Ship Faster with Soarias

Soarias ($79, one-time, local-first) integrates with Claude Code to scaffold your SwiftData schema, card UI, and SRS logic from a single prompt—skipping the repetitive boilerplate that typically consumes the first two days of an intermediate project. With automated screenshot generation and App Store metadata drafting built in, most developers go from blank Xcode project to TestFlight build in under 48 hours.

FAQ

Do I need an Apple Developer account?

You can build and run the app on the iOS Simulator for free. To install it on a physical device or submit to the App Store you'll need a paid Apple Developer account ($99/year). A free account can still sideload to your own device for testing.

How do I submit to the App Store?

Archive your app in Xcode (Product → Archive), then use the Organizer to upload to App Store Connect. Fill in the required metadata—app description, screenshots for each device size, and privacy nutrition labels—before submitting for review. Apple's review typically takes 24–48 hours for a new submission.

Last reviewed: 2026-05-12 by the Soarias team.