Creating a Sticker App with a Custom Layout

At a glance

Project structure

Source bundle/
├── Stickers/
│   ├── Stickers MessagesExtension/
│   │   ├── StickerCollectionReusableViews.swift
│   │   ├── MessagesViewController.swift
│   │   ├── Stickers+Extensions.swift
│   │   ├── Base.lproj/
│   │   │   └── MainInterface.storyboard
│   │   └── Info.plist
│   ├── Stickers.xcodeproj/
│   │   ├── .xcodesamplecode.plist
│   │   └── project.pbxproj
│   └── Stickers/
│       └── Info.plist
└── Configuration/
    └── SampleCode.xcconfig

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 6 project/configuration file(s) and 8 source declaration(s).

Overall architecture

flowchart LR
    N1["MessagesViewController"]
    N2["Messages APIs"]
    N1 --> N2

Reference code

Stickers/Stickers MessagesExtension/MessagesViewController.swift:11 — architecture anchor

class MessagesViewController: MSMessagesAppViewController {
    // ...
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into Messages.

Ownership and state

classDiagram
    TitleSupplementaryView *-- UILabel : label
    TextSupplementaryView *-- CustomField : field
    PictureSupplementaryView *-- UIButton : button
    CustomContentConfiguration o-- MSSticker : sticker

Ownership evidence

Stickers/Stickers MessagesExtension/StickerCollectionReusableViews.swift:11 — stored dependency or nearest verified ownership anchor

    let label = UILabel()
    static let reuseIdentifier = "title-supplementary-reuse-identifier"

    override init(frame: CGRect) {
        super.init(frame: frame)
        configure()
    }

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Class and protocol design

Stickers/Stickers MessagesExtension/StickerCollectionReusableViews.swift:10 — representative type boundary

class TitleSupplementaryView: UICollectionReusableView {
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

Stickers/Stickers MessagesExtension/MessagesViewController.swift:21 — representative boundary

class MessagesViewController: MSMessagesAppViewController {
    // ...
    private var collectionView: UICollectionView!
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: Controller: MessagesViewController; View: CustomContentView, PictureSupplementaryView, TextSupplementaryView, TitleSupplementaryView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: configure, textRect, editingRect, makeContentView, updated, setupInternalViews, apply, createLayout.
• Files: Stickers/Stickers MessagesExtension/MessagesViewController.swift.

Architecture takeaways

• MessagesViewController is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, Messages through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation