Introduction to Swift Programming Langauge

Welcome to Swift Programming Langauge

Swift is a new programming language for iOS and OS X apps that builds on the best of C and Objective-C, without the constraints of C compatibility. Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Swift’s clean slate, backed by the mature and much-loved Cocoa and Cocoa Touch frameworks, is an opportunity to reimagine how software development works.

Swift feels familiar to Objective-C developers. It adopts the readability of Objective-C’s named parameters and the power of Objective-C’s dynamic object model. It provides seamless access to existing Cocoa frameworks and mix-and-match interoperability with Objective-C code. Building from this common ground, Swift introduces many new features and unifies the procedural and object-oriented portions of the language.

Basic Values in swift Programming Language

Tradition suggests that the first program in a new language should print the words “Hello, world” on the screen. In Swift, this can be done in a single line:

println("Hello, world")

If you have written code in C or Objective-C, this syntax looks familiar to you—in Swift, this line of code is a complete program. You don’t need to import a separate library for functionality like input/output or string handling. Code written at global scope is used as the entry point for the program, so you don’t need a main function. You also don’t need to write semicolons at the end of every statement.

Simple Values

Use let to make a constant and var to make a variable. The value of a constant doesn’t need to be known at compile time, but you must assign it a value exactly once. This means you can use constants to name a value that you determine once but use in many places.

var myVariable = 42
myVariable = 50
let myConstant = 42

A constant or variable must have the same type as the value you want to assign to it. However, you don’t always have to write the type explicitly. Providing a value when you
create a constant or variable lets the compiler infer its type. In the example above, the compiler infers that myVariable is an integer because its initial value is a integer. If the initial value doesn’t provide enough
information (or if there is no initial value), specify the type by writing it after the variable, separated by a colon.

let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble: Double = 70

Values are never implicitly converted to another type. If you need to convert a value to a different type, explicitly make an instance of the desired type.

let label = "The width is "
let width = 94
let widthLabel = label + String(width)

There’s an even simpler way to include values in strings: Write the value in parentheses, and write a backslash (\) before the parentheses. For example:

let apple = 3
let oranges = 5
let appleSummary = "I have \(apples) apples."
let fruitSummary = "I have \(apples + oranges) pieces of fruit."