1 Week Plan

Structs are value types and get copied. Classes are reference types and are shared.

Value semantics means each copy is independent; copy-on-write makes copies cheap by sharing storage until someone mutates it.

An optional either holds a value or nil; unwrap it with if let, guard let, ?? or optional chaining instead of force unwrapping.

An escaping closure can be called after the function that received it returns, so it must be marked @escaping and you must think about what it captures.

Protocol-oriented programming means building behavior from small protocols with default implementations, instead of deep class inheritance.

Find the two numbers in an array that add up to a target, in one pass.

Check that every bracket in a string is closed by the same type, in the right order.

ARC counts strong references to each class instance and frees the instance as soon as the count reaches zero, with retain and release calls inserted by the compiler.

A strong reference keeps an object alive, a weak reference does not and becomes nil when the object dies, and an unowned reference does not and crashes if used after the object dies.

A retain cycle happens when objects hold strong references to each other so their counts never reach zero; you break it by making one link weak or unowned.

A capture list, like [weak self] or [count], controls how a closure captures values, either by making references weak or by copying a value at creation time.

Build a generic cache that drops the least recently used item when it is full. Every operation must be O(1).

Group words made of the same letters by using a dictionary with a smart key.

GCD is a lightweight C-based API for running closures on queues, while OperationQueue is a higher-level Objective-C API built on GCD that adds dependencies, cancellation and concurrency limits.

An async function can pause at each await without blocking its thread, letting Swift run other work on that thread until the result is ready.

An actor is a reference type that protects its mutable state by running only one task at a time on it, and reentrancy means its state can change while one of its methods is suspended at an await.

@MainActor is a global actor that runs code on the main thread, and marking UI types and methods with it lets the compiler check that UI updates happen there.

A deadlock is when threads wait for each other forever, a data race is unsynchronized access to the same memory with at least one write, and a race condition is a logic bug that depends on timing.

Run an action only after the calls stop for a short time, like a search box that waits until the user stops typing.

Build a bank account as an actor so many tasks can deposit, withdraw and transfer at the same time without data races.

A view controller creates its view, loads it once in viewDidLoad, then gets appear and disappear callbacks every time it shows or hides.

Auto Layout solves a set of constraint equations to find each view's frame, and hugging and compression resistance priorities decide which view grows or shrinks first.

A table view keeps a small pool of cells and reuses them for new rows, so you must fully reset each cell or you will see old data.

The @State wrapper owns data inside a view, @Binding gives a child read-write access to someone else's data, @Bindable makes bindings to an @Observable object, and @Environment reads shared values from above.

SwiftUI uses identity to decide if a view is the same one as before, and identity controls how long state lives and whether changes animate or reset.

Build an email and password form with live validation, a loading state, server errors and good keyboard focus.

MVC is simple but leads to huge view controllers, MVVM moves logic into a testable view model, VIPER splits a screen into many small roles, and TCA uses one state, actions and a reducer.

Dependency injection means an object gets its dependencies from outside instead of creating them, which makes code easy to test and change.

Build a URLRequest, call try await session.data(for:), check the HTTP status code, then decode the data, and choose a session configuration for caching, timeouts or background transfers.

Codable lets the compiler generate encoding and decoding code, and you customize it with CodingKeys, decoder strategies or a hand-written init(from:).

Decode a real-looking API response with snake_case keys, ISO 8601 dates, nested and optional fields, and an enum that survives new values.

Retry a failing async operation, and double the wait time after each failure.

When to use two pointers, sliding window, hashing, binary search and prefix sums, with a short Swift template for each.

Merge overlapping calendar events into busy blocks by sorting first, then scanning once.

Count how often each hashtag is used and return the k most popular ones.

Find the longest run of unique characters with a sliding window and a dictionary.

Reverse a singly linked list in place by turning every next pointer around.

Count connected regions of filled pixels in a mask with flood fill (the "number of islands" problem).

A step-by-step plan for the round, with time boxes, what to say at each step, and a worked example.

Build a Kingfisher-style library with a memory and disk cache, shared in-flight requests, downsampling, and safe cancellation in reused cells.

Design a social feed with cursor pagination, prefetching, optimistic likes and an offline cache that opens instantly.

Build a list that loads the next page before the user reaches the end, with loading, error and empty states.

How to answer "Tell me about a time…" questions with the STAR method, with 10 common questions and short sample answers from iOS work.