Objective-C

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What you'll learn

Objective-C is the language that powered iOS and macOS for two decades and still sits underneath UIKit, Foundation, and every framework SwiftUI is built on. This tier is a standalone reference — not an app-building ladder — that takes you from syntax foundations through message passing, memory management, blocks, categories, protocols, and the modern patterns you need to read legacy code and interoperate with Swift.

Who is this for?

Who is this for?

Developers who want to read and maintain Objective-C codebases, understand the runtime that UIKit still depends on, or bridge between Objective-C and Swift. No prior iOS experience required.

The ladder

1. 01 Why Objective-C — what Objective-C is, where it still lives, and why it matters today.
2. 02 Syntax foundations — headers, implementations, message passing, and the C underpinnings.
3. 03 Classes and objects — defining classes, properties, and instantiating objects.
4. 04 Memory management — ARC, retain cycles, strong/weak references, and autorelease pools.
5. 05 Categories and protocols — extending existing classes and defining contracts.
6. 06 Foundation essentials — NSString, NSArray, NSDictionary, NSNumber, and the core collections.
7. 07 Blocks — Objective-C's closures, capture semantics, and memory pitfalls.
8. 08 UIKit with ObjC — view controllers, views, and the responder chain in Objective-C.
9. 09 Error handling — NSError, out parameters, and the error domain pattern.
10. 10 KVO and NotificationCenter — observing changes without bindings.
11. 11 ObjC-Swift interop — bridging headers, module maps, and annotation.
12. 12 Testing ObjC code — XCTest in Objective-C and common fixtures.

Prerequisites

None — this is a standalone language reference.

Start → 01 Why Objective-C