creating-extension

name	creating-extension
description	Create a Swift extension file with the Type+EXT.swift naming convention in the Extensions/ folder. Use when the user asks to add an extension, add a helper method to an existing type, or extend a Foundation/SwiftUI/custom type.

Creating Extension

Create a Swift extension file following the project's naming and folder conventions.

Steps

1. Identify the type being extended (e.g., String, Color, Array, a custom model type)
2. Check if Extensions/{TypeName}+EXT.swift already exists — if so, add to that file instead of creating a new one
3. If new, create the file in SwiftfulStarterProject/Extensions/

File Naming

All extension files follow: {TypeName}+EXT.swift

Examples: String+EXT.swift, Color+EXT.swift, Date+EXT.swift, UserModel+EXT.swift

Template

import SwiftUI

extension {TypeName} {

}

Key Patterns

• Always check first if {TypeName}+EXT.swift already exists — add to it rather than creating a duplicate
• One file per type — group all extensions for a type in a single +EXT file
• Multiple extension blocks in the same file are fine for grouping related functionality
• Import: use import SwiftUI (covers Foundation) unless the extension only needs import Foundation
• Access level: use public only if the type itself is public (e.g., public extension Color), otherwise use default internal access
• No business logic — extensions add convenience methods, computed properties, and static helpers, not app logic
• Prefer after-object notation — myValue.doSomething() over DoSomething(myValue) (instance methods over free functions)
• Prefer computed properties when there are no parameters — myValue.asString over myValue.asString()
• Be explicit with naming — do NOT abbreviate or shorten names, clarity over brevity (e.g., replaceSpacesWithUnderscores not replaceSpaces)