Swift is a powerful and intuitive programming language developed by Apple for building iOS, macOS, watchOS, and tvOS applications. It was first introduced in 2014 and has since become one of the most popular programming languages in the world.
Swift is designed to be easy to learn and use, with a syntax that is concise and expressive. It is also highly efficient, with performance that is comparable to that of C++ and Objective-C. This makes it an ideal choice for developing high-performance applications that run smoothly on Apple devices.
This cheat sheet provides an overview of the most important concepts and syntax in Swift. It is divided into different sections for easy navigation.
Basics
Syntax Description var variableName: Type = valueDeclares a variable with an initial value let constantName: Type = valueDeclares a constant with an initial value func functionName(parameterName: Type) -> ReturnTypeDeclares a function with a parameter and return type if condition { ... } else { ... }Executes code based on a condition for item in collection { ... }Loops over a collection of items while condition { ... }Loops while a condition is true switch value { case pattern: ... }Executes code based on a value matching a pattern guard condition else { ... }Exits a function if a condition is not met try expressionExecutes an expression that can throw an error do { ... } catch { ... }Handles errors thrown by an expression
Optionals
Syntax Description var optionalValue: Type?Declares an optional variable optionalValue = nilSets an optional variable to nil if let unwrappedValue = optionalValue { ... }Unwraps an optional value if it is not nil guard let unwrappedValue = optionalValue else { ... }Exits a function if an optional value is nil optionalValue ?? defaultValueReturns a default value if an optional value is nil
Collections
Syntax Description var array: [Type] = [value1, value2, ...]Declares an array array.append(value)Adds a value to an array array.remove(at: index)Removes a value from an array var dictionary: [KeyType: ValueType] = [key1: value1, key2: value2, ...]Declares a dictionary dictionary[key] = valueAdds a key-value pair to a dictionary dictionary.removeValue(forKey: key)Removes a key-value pair from a dictionary
Classes and Structs
Syntax Description class ClassName { ... }Declares a class struct StructName { ... }Declares a struct var instance = ClassName()Creates an instance of a class var instance = StructName()Creates an instance of a struct class ClassName: SuperclassName { ... }Declares a subclass struct StructName: Protocol1, Protocol2 { ... }Declares a struct that conforms to multiple protocols init(parameterName: Type) { ... }Declares an initializer deinit { ... }Declares a deinitializer var property: Type = valueDeclares a property func methodName(parameterName: Type) -> ReturnType { ... }Declares a method
Closures
Syntax Description { (parameters) -> ReturnType in ... }Declares a closure array.map { (item) -> ReturnType in ... }Applies a closure to each item in an array array.filter { (item) -> Bool in ... }Filters an array based on a closure array.reduce(initialValue) { (result, item) -> ReturnType in ... }Reduces an array to a single value based on a closure
References