Access control (public/internal/fileprivate/private)
Control visibility of APIs across files and modules using public, internal (default), fileprivate, and private. Learn when to expose vs hide.
Access control (public/internal/fileprivate/private) is a free Swift Academy lesson on CoddyKit. This is lesson 3 of 3. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 3 lessons in total.
Access levels overview
Swift access levels:
- public: visible to other modules
- internal (default): visible in the same module
- fileprivate: only this source file
- private: enclosing scope (type/extension)
internal (default)
Omitting a modifier makes declarations internal, usable anywhere within the same module (package/app target).
struct Greeter { // internal by default
func hello(_ name: String) -> String { "Hello, \\(name)" }
}
let g = Greeter()
print(g.hello("Ada"))public API surface
Mark APIs public to expose them to other modules; leave helpers internal to keep surface area small.
public struct Math {
public static func add(_ a: Int, _ b: Int) -> Int { a + b }
// internal helper remains hidden outside the module
static func double(_ x: Int) -> Int { x * 2 }
}
print(Math.add(1,2))fileprivate scope
fileprivate restricts use to the same source file. Great for splitting helpers for a type inside one file.
// In FileA.swift
fileprivate func hiddenInFile() { print("Only in this file") }
struct A {
func call() { hiddenInFile() } // OK: same file
}
A().call()private scope
private limits access to the enclosing scope (type/extension). Use it to protect invariants tightly.
struct Box {
private var value = 0 // visible only inside Box declaration
mutating func set(_ v: Int) { value = v } // controlled write
func get() -> Int { value } // controlled read
}
var b = Box()
b.set(7)
print(b.get())
// b.value = 3 // error: 'value' is privateDesign tips
Design tips:
- Default to internal, expose only what consumers need as public.
- Prefer private/fileprivate for helpers to keep APIs small.
- Access level of a member cannot be broader than its type.
Default access
Quick check: What's the default access level?
Recap
Recap: Use public to expose modules, keep most things internal, and hide details with fileprivate/private to protect invariants.
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Frequently Asked Questions
Is the “Access control (public/internal/fileprivate/private)” lesson free?
Yes — any 3 lessons of the Swift Academy learning path, including “Access control (public/internal/fileprivate/private)”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 3 lessons in total.
What will I learn in “Access control (public/internal/fileprivate/private)”?
Control visibility of APIs across files and modules using public, internal (default), fileprivate, and private. Learn when to expose vs hide. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Swift Academy?
No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 3 of 3.
How long does the “Access control (public/internal/fileprivate/private)” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Swift Academy lesson?
Yes. Every Swift Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Memberwise init & mutating methods
- Inheritance, overriding & final
- Access control (public/internal/fileprivate/private)