QRCodeGen

A Swift iOS QR Code Generator app made with SwiftUI that meets the ISO/IEC 18004 specification for QR codes. The app is made using Core Image.

Architecture

The app follows a layered, testable design. The view owns no business logic; everything flows through an @Observable view model that depends only on protocols, so each layer is replaceable and unit-testable in isolation.

App/ Composition root — builds the dependency graph and SwiftData container
Models/ QRCodeRequest, QRAppearance, ErrorCorrectionLevel, QRCodeError (typed)
Services/ QRCodeGenerating → CoreImageQRCodeGenerator (rendering)
ImageExporting → LiveImageExporter (clipboard / Photos)
HistoryStoring → SwiftDataHistoryStore (persistence)
Persistence/ QRHistoryEntry (@Model)
ViewModels/ QRGeneratorViewModel (@Observable, @MainActor)
Views/ ContentView shell + focused section views

Key decisions

Decision	Why
@Observable view model, no Combine	Modern Swift state with async/await; no reactive framework needed for one screen.
Protocol seams (QRCodeGenerating, ImageExporting, HistoryStoring)	The view model depends on abstractions, so tests inject mocks — no Core Image, UIKit, or disk required.
Plain AppDependencies struct for DI	Init-injection with a live default is the idiomatic "container"; no third-party DI framework.
Typed QRCodeError: LocalizedError	Replaces untyped NSError; call sites switch on cases and tests assert exact failures.
Single image source of truth	The view model stores one UIImage and derives the SwiftUI Image, eliminating a class of sync bugs.
SwiftData behind HistoryStoring	SwiftData is an implementation detail, not the architecture — the view model never imports it.
Off-main, Sendable generator	Rendering is CPU-bound; the generator is nonisolated/async so the main thread stays responsive.

Brief Explanation of Technical Background of QR Codes

QR codes (Quick Response codes) are two-dimensional barcodes that store information in a grid of black and white squares. Originally developed in 1994 by Denso Wave for tracking automotive parts in manufacturing, QR codes have become ubiquitous for quickly sharing URLs, contact information, and other data through smartphone cameras. The "QR" name reflects their design goal: to be decoded at high speed.

A QR code consists of several key components:

• Finder patterns (the large squares in three corners that help scanners locate and orient the code).
• Alignment patterns (smaller patterns that assist with reading larger codes).
• Timing patterns (alternating modules that help determine the code's size).
• Data area (where the actual encoded information is stored).
• Error correction data (allowing the code to remain readable even when partially damaged or obscured).

Text Encoding Modes:

• Numeric: Digits 0 through 9.
• Alphanumeric: Decimal digits 0 through 9, as well as uppercase letters, and the symbols $, %, *, +, -, ., /,:, and space.
• Byte: Characters from the ISO-8859-1 character set. ISO-8859-1 (aka Latin-1) is a single-byte character encoding standard for representing Western European languages, including characters, digits, and symbols.
• Kanji: Double-byte characters from the Shift JIS character set. The Shift JIS character set is a character encoding standard for the Japanese language that uses a combination of one- and two-byte characters.

Screenshots

Here are some screenshots showcasing the app's features:

Generator screen	Text input	Generated code	Save & share	History detail

Generator screen	Text input	Generated code	Save & share	History detail

Language, Frameworks, & Tools used:

• Swift 6 (strict concurrency, default @MainActor isolation)
• SwiftUI + Observation (@Observable)
• SwiftData (history persistence)
• iOS 27 / Xcode 27
• Core Image (CIQRCodeGenerator, CIFalseColor)
• PhotosUI / Photos
• Swift Testing (unit) + XCTest / XCUIAutomation (UI)
• SwiftLint
• GitHub Actions (CI)

Requirements

Error Correction Level

Error Correction Level	Error Correction Capability
L	Recovers 7% of data
M	Recovers 15% of data
Q	Recovers 25% of data
H	Recovers 30% of data

Smallest QR Code Version

Error Correction Level	Numeric Mode	Alpha Numeric Mode	Byte Mode	Kanji Mode
L	187	114	78	48
M	149	90	62	38
Q	111	67	46	28
H	82	50	34	21

Features

• High-Quality QR Code Generation – Powered by Apple’s CIQRCodeGenerator (Core Image)

  • Automatically selects optimal version
  • Full support for L, M, Q, H error correction levels
  • Perfectly compliant with ISO/IEC 18004 standard

• Smart Input Handling

  • Paste from clipboard with one tap
  • Clear button for instant reset
  • Multi-line text input with vertical expansion

• Error Correction Picker

  • Segmented control with descriptive labels:
    Low (7%) | Medium (15%) | Quartile (25%) | High (30%)
  • Real-time resilience feedback in UI

• Appearance Customization

  • Foreground & background color pickers (via Core Image CIFalseColor)
  • Adjustable module size (6–20 px), clamped to stay scannable
  • Live, debounced restyle of the current code

• Generation History (SwiftData)

  • Recent generations persisted across launches
  • Tap to restore a code's text, error-correction level, and appearance
  • Swipe to delete

• Beautiful, Scalable Output

  • Configurable module size + 4-module quiet zone composited over the background color
  • High-resolution CGImage → UIImage pipeline
  • Smooth interpolation disabled for pixel-perfect QR modules

• Rich Interaction & Sharing

  • Tap-and-hold context menu:
    • Copy to clipboard
    • Save to Photos
    • Share via ShareLink
  • Toolbar actions: Paste, Clear, Share
  • Haptic feedback on success/error

• Modern SwiftUI Design

  • NavigationStack + List with .insetGrouped style
  • Glass morphism button (.glassEffect)
  • Adaptive dark/light mode previews
  • Accessibility labels & hints throughout

• Robust Generation Flow

  • Debounced input (350ms) to prevent spam
  • Cancelable Task for smooth UX
  • Error display with localized messages
  • ProgressView during generation

• Zero External Dependencies

  • Uses only Apple frameworks: SwiftUI, Observation, SwiftData, CoreImage, Photos/PhotosUI, UniformTypeIdentifiers

Testing

The suite is split by what it verifies, and the seams above make the business logic testable without UIKit, Core Image, or disk.

Suite	Layer	Coverage
QRGeneratorViewModelTests	View model	Generation success/failure, history recording, empty-input rules, export forwarding, restore — driven entirely through mocks.
CoreImageQRCodeGeneratorTests	Rendering	Determinism, error-correction sensitivity, empty input, module-size scaling, and tinting.
HistoryStoreTests	Persistence	Add / fetch / ordering / fetch-limit / delete / clear against an in-memory SwiftData container.
ModelTests	Models	Appearance clamping, Codable round-trip, and Color↔hex bridging.
QRCodeFlowUITests	UI	End-to-end flows via accessibility identifiers (generate, context menu, toolbar, ECL switching).

Unit tests use Swift Testing (@Suite/@Test/#expect); UI tests use XCUIAutomation (XCTest), the supported path for XCUIApplication.

License

Released under the MIT License. © 2026 SarahUniverse