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Subjects

JAVASCRIPTHTMLCSSPYTHONSQLJAVACPPCSHARPPHPTYPESCRIPTCRUBYGOSWIFTKOTLINRUSTRBASHSCALAOBJECTIVE-CDARTPERLLUAMATLABXMLJSONMARKDOWNASSEMBLYLATEXYAMLSOLIDITYBLOCKCHAIN

Topics

Swift Basics

Introduction to SwiftSwift Development EnvironmentSwift SyntaxSwift Variables and ConstantsSwift Data TypesSwift OperatorsSwift CommentsSwift Type InferenceSwift Type SafetySwift OptionalsSwift Optional BindingSwift Tuples

Control Flow

Swift If-Else StatementsSwift Switch StatementsSwift For LoopsSwift While LoopsSwift Repeat-While LoopsSwift Break and ContinueSwift Guard StatementsSwift Defer Statements

Functions and Closures

Swift FunctionsSwift Function ParametersSwift Return ValuesSwift Variadic ParametersSwift In-Out ParametersSwift Function TypesSwift Nested FunctionsSwift ClosuresSwift Trailing ClosuresSwift Capturing Values

Collections and Enumerations

Swift ArraysSwift SetsSwift DictionariesSwift Collection OperationsSwift EnumerationsSwift Raw Value EnumerationsSwift Associated Values

Object-Oriented Programming

Swift ClassesSwift StructuresSwift PropertiesSwift MethodsSwift InheritanceSwift InitializationSwift DeinitializationSwift Access ControlSwift Type CastingSwift Nested Types

Protocols and Extensions

Swift ProtocolsSwift Protocol ConformanceSwift Protocol ExtensionsSwift DelegationSwift ExtensionsSwift Generic Protocols

Error Handling and Debugging

Swift Error HandlingSwift Do-Try-CatchSwift AssertionsSwift PreconditionsSwift Debugging Techniques

Generics

Swift Generic FunctionsSwift Generic TypesSwift Type ConstraintsSwift Associated TypesSwift Generic Where Clauses

Memory Management

Swift ARCSwift Strong Reference CyclesSwift Weak ReferencesSwift Unowned ReferencesSwift Capture Lists

Concurrency

Swift Grand Central DispatchSwift Operation QueuesSwift Async/AwaitSwift ActorsSwift Task GroupsSwift Sendable Protocol

Swift Standard Library

Swift String ManipulationSwift Number and Math OperationsSwift Date and TimeSwift Sequence and CollectionSwift Codable ProtocolSwift Result Type

Swift and Objective-C

Swift and Objective-C InteropSwift Bridging Header@objc and dynamicSwift Selector

Advanced Swift

Swift Property WrappersSwift Custom OperatorsSwift SubscriptsSwift Key PathsSwift MetatypeSwift Phantom TypesSwift Result Builders

Swift Variables and Constants

In Swift, variables and constants are fundamental building blocks for storing and manipulating data. They play a crucial role in managing information throughout your program.

Variables

Variables are containers that hold values which can be changed during program execution. They are declared using the var keyword.

var age = 25
age = 26 // Value can be changed

Constants

Constants, on the other hand, hold values that cannot be modified once they are assigned. They are declared using the let keyword.

let pi = 3.14159
// pi = 3.14 // This would result in an error

Type Inference and Explicit Type Declaration

Swift uses Type Inference to automatically determine the data type of a variable or constant based on its initial value. However, you can also explicitly declare the type:

var name: String = "John"
let height: Double = 1.75

When to Use Variables vs Constants

  • Use variables when the value needs to change over time
  • Use constants for values that should remain fixed
  • Prefer constants by default for better code safety and performance

Naming Conventions

Swift uses camelCase for naming variables and constants. Names should be descriptive and meaningful:

let maximumLoginAttempts = 3
var currentLoginAttempt = 0

Multiple Declaration

You can declare multiple variables or constants of the same type in a single line:

var x = 0.0, y = 0.0, z = 0.0

Type Safety

Swift is a type-safe language. This means you can't assign a value of one type to a variable or constant of another type. For more information, see Swift Type Safety.

Optionals

In Swift, you can use Optionals to represent the absence of a value. This is particularly useful when working with variables that might not have a value:

var possibleNumber: Int? = nil
possibleNumber = 42

Best Practices

  • Use meaningful and descriptive names for variables and constants
  • Prefer constants over variables when the value won't change
  • Use type inference when possible, but explicitly declare types when needed for clarity
  • Consider using optionals when a variable might not have a value

Understanding variables and constants is crucial for effective Swift programming. They form the foundation for more advanced concepts like Swift Data Types and Swift Operators.