300+ Questions: Mastering the IOS Technical Interview

Discover multiple approaches to laying out UIView elements, from interface builder with storyboards to code-based layouts using exact CGRect coordinates, including options to work without storyboards.

Explore the main concurrency approaches in iOS and macOS, including Grand Central Dispatch, dispatch queues, and operation queues, with their strengths, weaknesses, and when to choose each.

Compare assign vs retain: assign is used for scalar types like float and does not own the value, while retain denotes ownership and can be dynamic based on the situation.

Explore how Cocoa and Cocoa Touch enable mac and iOS app development via the Objective-C runtime, with Cocoa containing Foundation and AppKit and Cocoa Touch containing Foundation and UIKit.

Describe a managed object context as a temporary scratchpad for fetched objects, providing an internally consistent view; modify objects within the context, but the persistence store stays unchanged until saved.

Learn how to add iOS frameworks, switch from product to target, drag and drop frameworks, and then check the directory to ensure they are added in the proper location.

Store private user data securely on device offline using keychain with pin codes or encrypted databases, and consider remote servers over ssl with certificate pinning and data validation.

Discover how iBeacons use Bluetooth Low Energy to let mobile apps listen for beacon signals in the physical world, determine precise location, and deliver contextual content to users.

Explore SpriteKit and SceneKit as iOS frameworks that simplify game development, enable 3D graphics, object and physics property manipulation, and on-screen rendering to produce games.

Compare Swift and Objective-C, highlighting Objective-C's dynamic runtime and C heritage, Swift's safer, type-safe syntax, bridging between them, and the value of knowing both for legacy code.

Describe how an iOS app transitions from locked or not running into inactive, then into active and background states upon launch, before briefly reaching the suspended state.

Explore how strong and weak references govern memory management, how mutual strong references cause memory leaks, and why Interface Builder uses weak references to prevent cycles.

Understand how reuse identifiers group similar table rows and recycle cells to allocate memory only for visible content during scrolling.

Learn how to replace c-style loops with a stride function to iterate from zero to ten by one, printing each value.

Explore how a wildcard app id uses an asterisk to represent variable parts, enabling a bundle of apps with the same prefix to fall under one app id.

Identify common reasons for App Store rejection, including bugs, crashes, broken links, placeholder content, incomplete or misleading descriptions, noncompliant UI, and excessive ads, to improve submission quality.

Master the process to push an app to the App Store, including creating the bundle identifier, certificate signing request, production certificate, provisioning profile, listing details, SEO tactics, versioning, and submission.

Explain the differences between developer and enterprise accounts, focusing on distribution, access, and cost. Note the $99 developer fee and enterprise pricing of 2.9 per year, for internal crm apps.

Compare viewDidLoad and viewDidAppear for loading remote server data. Choose caching for static data and refreshing for frequently changing data to balance real-time needs.

Wait for a thread to finish before starting another using a selector on the main thread, keeping the user interface responsive with a busy indicator until data updates.

Explore UI controls by examining concrete subclasses like buttons, segment controls, and switches, and learn how properties, functions, and selectors trigger events and handle data properties.

Discover how to execute code while an iOS app runs in the background by registering a background task with a 10–15 minute limit, enabling downloads to continue after suspension.

Explore common iOS UI elements such as buttons, text fields, images, and labels, and learn how to implement them with Interface Builder, code from scratch, or layout constraints.

Compare unit tests with UI testing and learn to isolate a unit’s features, functions, and methods to run a focused test suite that validates pure code functionality.

Explore SQLite, a lightweight, self-contained engine with fast performance, iOS and Mac OS support, and strong community backing, though not as robust as sequel server.

Categories extend functionality by adding methods to an existing class, such as in the Cocoa framework, distribute implementations across separate files, and group large methods into categories for modular code.

Master four major data types: string, floats, integers, and booleans; learn their characteristics, such as strings of characters, floats as decimal numbers, and booleans as true or false.

Explain how the dynamic keyword enables runtime message interception in Objective-C and how a superclass property outlet is wired in a subclass.

Explore the differences between include and import: include may duplicate a file, while import reads it once, with header protections preventing multiple inclusions.

Explain formal protocols in ObjC and how they declare required or optional methods, adoption in type checking, and inheritance from ancestors. Include informal protocols and how they influence protocol design.

Explore the difference between synchronous and asynchronous blocks using perform block, showing how execution order changes and when the program waits for a block to finish on a separate thread.

Learn why atomic properties guarantee fully initialized values by default, and see how non-atomic options trade safety for performance when a precise value isn't required.

Learn to work with crash logs by locating and importing x-archive files, matching exact version strings from the application properties, and organizing crash data in the crash logs devices window.

Discover persistence stores, including in-memory, light stores, and binary stores, and learn when to use each type for readability, performance, and atomic data handling in large datasets.

Explain how the persistent store coordinator links stores to the core data model and mediates between stores and the managed object context in the core data stack.

Determine when code is thread safe by ensuring correct behavior under simultaneous execution of multiple threads regardless of scheduling interleaving, with no additional synchronization or coordination in the calling code.

Learn when to use weak references for self in a block, and how to adopt a strong self inside the block to avoid retain cycles and premature deallocation.

Examine ARC, a memory management feature that uses retain and release to manage reference counts and deallocate objects when zero, contrasting with garbage collection and promoting weak references.

Explain the difference between copy and retain: retain increments the object's retain count and preserves ownership, while copy creates a new data copy and assigns it to a new variable.

Explore the difference between strong and retain in memory management, showing they are virtually the same in use and why retain remains a legacy convenience from older days.

Master iOS memory management by guiding object lifecycles and freeing memory when no longer needed, and focus on breaking reference cycles to deallocate and use less memory.

Identify retain cycles that cause memory leaks by understanding mutual references and use instruments and tools to detect and prevent memory release failures.