Customizing an image picker controller

At a glance

Project structure

PhotoPicker/
├── AppDelegate.swift
├── ViewController.swift
├── Base.lproj/
│   ├── Main.storyboard
│   └── LaunchScreen.storyboard
├── Assets.xcassets/
└── Info.plist

Structure observations

• ViewController.swift owns the entire camera/photo-picker feature; there is no separate camera service or session model.
• The storyboard supplies the main image view, camera overlay, and toolbar button outlets.
• AVFoundation is used only for camera authorization; capture itself goes through UIImagePickerController.

Overall architecture

flowchart LR
    Toolbar["Main toolbar action"] --> Controller["APLViewController"]
    Controller -->|"authorization check"| CameraAuth["AVCaptureDevice"]
    Controller --> Picker["UIImagePickerController"]
    Overlay["Storyboard overlayView"] --> Picker
    OverlayAction["Take / Delay / Interval / Done"] --> Controller
    Controller --> Timer["Timer"]
    Timer -->|"takePicture"| Picker
    Picker -->|"delegate image / cancel"| Controller
    Controller --> Captures["capturedImages"]
    Captures --> Display["imageView / animationImages"]

Reference code

PhotoPicker/ViewController.swift:167 — source type selects presentation style; camera mode disables standard controls and installs the storyboard overlay before presentation.

imagePickerController.sourceType = sourceType
imagePickerController.modalPresentationStyle =
    sourceType == .camera ? .fullScreen : .popover

let presentationController =
    imagePickerController.popoverPresentationController
presentationController?.barButtonItem = button

if sourceType == .camera {
    imagePickerController.showsCameraControls = false
    overlayView?.frame =
        (imagePickerController.cameraOverlayView?.frame)!
    imagePickerController.cameraOverlayView = overlayView
}

present(imagePickerController, animated: true)

Interpretation

The app customizes a system-owned capture workflow rather than building an AVCaptureSession. APLViewController is both composition root and session coordinator: it chooses the picker mode, injects the overlay, translates overlay actions into picker commands, and consumes delegate results.

Ownership and state

classDiagram
    APLViewController *-- UIImagePickerController : long-lived picker
    UIImagePickerController --> APLViewController : delegate reference
    APLViewController o-- UIView : overlay IBOutlet
    UIImagePickerController o-- UIView : cameraOverlayView while presented
    APLViewController *-- Timer : capture schedule
    Timer --> APLViewController : block callback
    APLViewController *-- UIImageArray : capturedImages
    APLViewController o-- UIImageView : result outlet

Ownership evidence

PhotoPicker/ViewController.swift:13 — the controller stores all visual connections plus the picker, timer, and captured-image buffer.

@IBOutlet var imageView: UIImageView?
@IBOutlet var cameraButton: UIBarButtonItem?
@IBOutlet var overlayView: UIView?
@IBOutlet var takePictureButton: UIBarButtonItem?
@IBOutlet var startStopButton: UIBarButtonItem?
@IBOutlet var delayedPhotoButton: UIBarButtonItem?
@IBOutlet var doneButton: UIBarButtonItem?

var imagePickerController = UIImagePickerController()
var cameraTimer = Timer()
var capturedImages = [UIImage]()

The timer and its closure make lifecycle explicit: repeating work must be invalidated before finishing the capture session.

Class and protocol design

There is no app-defined protocol. The framework delegate is the inversion point: the picker owns the interaction flow, then calls the controller with an image or cancellation.

Access control

Reference code

PhotoPicker/ViewController.swift:337 — the only explicit privacy boundary contains compatibility utilities used solely by picker-result handling.

private func convertFromUIImagePickerControllerInfoKeyDictionary(
    _ input: [UIImagePickerController.InfoKey: Any]
) -> [String: Any] {
    Dictionary(uniqueKeysWithValues:
        input.map { key, value in (key.rawValue, value) })
}

private func convertFromUIImagePickerControllerInfoKey(
    _ input: UIImagePickerController.InfoKey
) -> String {
    input.rawValue
}

Logic ownership and placement

Design patterns

Naming conventions

• APLViewController uses Apple’s older “APL” sample prefix rather than a feature-specific type name.
• Actions use explicit verbs: showImagePickerForCamera, takePhoto, delayedTakePhoto, and stopTakingPicturesAtIntervals.
• State names reveal lifecycle: cameraTimer and capturedImages.
• finishAndUpdate combines two responsibilities in its name because it both dismisses and updates the result view.

Architecture takeaways

• Customize a system controller through its supported overlay and delegate seams before building a lower-level capture stack.
• Keep one clear owner for picker, timer, capture buffer, and presentation.
• Treat repeating timers as owned resources that must be invalidated on every finish path.
• Framework delegate methods are sufficient here; an app-defined abstraction would only be justified when capture logic must be reused or tested independently.
• The sample’s module-wide state is pedagogical, not a model of minimal access control.

Source map

• Official Apple documentation