Swift Programming Concepts Overview

Overview

This lecture gives an in-depth introduction to core Swift programming concepts, covering variables, operators, control flow, functions, closures, structures, enumerations, classes, protocols, extensions, generics, optionals, error handling, collections, hashing, custom operators, and asynchronous programming.

Setting Up & Course Prerequisites

• The course is designed for those already familiar with programming basics in another language.
• Swift playgrounds are used for immediate code feedback; Xcode is recommended on Mac, though Linux with Swift and Visual Studio Code also works.
• A workspace in Xcode is a container for projects, files, and playgrounds.

Variables & Constants

• Use let for constants (cannot reassign or mutate) and var for variables (can reassign and mutate).
• Value types (like structs and arrays) are copied when assigned; reference types (like classes) share memory.
• Mutability depends on both let/var and the type (value vs. reference).

Operators

• Swift has unary prefix, unary postfix, binary infix, and ternary operators.
• Binary infix operators (+, -, *, /) act between two values.
• Ternary operator: condition ? valueIfTrue : valueIfFalse
• Logical operators combine conditions with && (and), || (or).*

Control Flow: If-Else & Switch

• if, else if, and else statements control execution flow according to conditions.
• Parentheses clarify complex logical conditions.
• switch statements provide exhaustive checks, especially useful with enums.

Functions

• Defined with func, can have parameters and return values.
• Functions can have default parameter values and internal/external parameter names.
• Mark a function as @discardableResult to ignore its result.

Closures

• Closures are inline functions, can be passed as parameters.
• Support trailing closure syntax for concise code.
• Use $0, $1 for shorthand closure arguments.
• Closures can capture variables from their surrounding scope.

Structures (Structs)

• Group related data and behaviors; are value types (copied on assignment).
• Custom initializers and computed properties can be defined.
• Use mutating keyword to allow property mutation within a struct's methods.

Enumerations (Enums)

• Define related value sets via cases.
• Support associated values (data attached to cases) and raw values (like strings/ints).
• Switch statements can unpack associated values for pattern matching.

Classes & Reference Types

• Classes are reference types (shared memory on assignment).
• Support inheritance and require explicit initializers.
• Mark properties with private(set) for read-only access outside the class.
• Deinitializers (deinit) run when an instance is deallocated.

Protocols

• Protocols define a blueprint for properties and methods; similar to interfaces in other languages.
• Types conform to protocols by implementing required methods/properties.
• Protocol extensions provide default implementations.

Extensions

• Extend existing types with new methods, properties, or protocol conformance.
• Add initializers or computed properties via extensions.

Generics

• Use generic types to write flexible, reusable code for multiple data types.
• Protocols can require an associatedtype for generic behavior.

Optionals

• Use ? for values that may be absent (nil).
• Unwrap optionals safely with if let or guard let.
• Optional chaining accesses deep properties if each link is non-nil.

Error Handling

• Use throws and try to manage errors.
• Handle errors with do-catch blocks, specifying error types.
• Use Result<Success, Failure> for error reporting without throwing.

Collections: Arrays, Sets, Dictionaries

• Arrays: ordered lists, accessed by index, support mutating methods (e.g., append).
• Sets: unordered, unique values, require elements to be Hashable.
• Dictionaries: key-value pairs, keys must be unique.

Equality & Hashing

• Implement Equatable for custom equality (==).
• Implement Hashable to customize how instances are hashed (for sets/dictionaries).

Custom Operators

• Define new operators with specific syntax for custom types.
• Specify prefix, postfix, or infix as needed.

Asynchronous Programming

• Async functions use async and await for non-blocking code execution.
• Use Task and async let for running concurrent operations.

Key Terms & Definitions

• let — Immutable constant.
• var — Mutable variable.
• Struct — Value type grouping properties and methods.
• Class — Reference type supporting inheritance.
• Protocol — Blueprint defining required functionality.
• Extension — Adds functionality to existing types.
• Generic — Type-agnostic code via placeholders.
• Optional — Value that could be nil.
• Result — Enum for success or failure outcome.
• Hashable — Protocol for unique object identification.
• Equatable — Protocol for defining equality.
• Closure — Inline function/object.
• Async/Await — Concurrency primitives for asynchronous execution.

Action Items / Next Steps

• Practice creating playgrounds and writing Swift code for each concept discussed.
• Review each Swift concept in the playground, focusing on understanding mutability, value vs. reference types, and error handling.
• Read official Swift documentation on structures, classes, protocols, optionals, and async/await for deeper understanding.