Swift Programming - Basic Syntax

Swift Programming - Basic Syntax

Lets start with Swift programming syntax. 

Find below Hello World Example in Swift

import Cocoa

/* My first program in Swift */

var myString = "Hello, World!"

println(myString)

Here in above example shows how to print "hello world". Here we have to import Cocoa instead of UIKit of Objective C. Check below code how we write for Swift.

import UIKit

var myString = "Hello, World!"

println(myString)

We must have to import UIKit for Objective C. After compile this code we will get the output

Hello World

Import in Swift

You can use the import statement to import any Objective-C framework into your Swift program. For example, the above import cocoa statement makes all Cocoa libraries, APIs, and runtimes that form the development layer for all of OS X, available in Swift.

Cocoa is implemented in Objective-C, which is a superset of C, so it is easy to mix C and even C++ into your Swift applications.

Tokens in Swift

A Swift program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following Swift statement consists of three tokens −

println("test!")

The individual tokens are:

println (

   "test!"

)

Comments

Comments helps texts in your Swift program. They are ignored by the compiler. 

Single Line Comment

// My first program in Swift is Hello, World!

Multiline Comment

Multi-line comments start with /* and terminate with the characters */ as shown below −

/* My first program in Swift */

Multi-line comments also allowed in Swift

/*

/* Nested Comments */

Semicolon

Swift doesn't require semicolon(;) after statement.

Identifiers

A Swift identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with an alphabet A to Z or a to z or an underscore _ followed by zero or more letters, underscores, and digits (0 to 9).

Swift does not allow special characters such as @, $, and % within identifiers. Swift is a case sensitive programming language. Thus, Manpower and manpower are two different identifiers in Swift. 

Here are some examples of acceptable identifiers −

Azad       zara    abc   move_name  a_123

myname50   _temp   j     a23b9      retVal

To use a reserved word as an identifier, you will need to put a backtick (`) before and after it. For example, class is not a valid identifier, but `class` is valid.

Keywords

The following keywords are reserved in Swift. These reserved words may not be used as constants or variables or any other identifier names, unless they're escaped with backticks −

Keywords used in declarations

class	deinit	enum	extension
func	import	init	internal
let	operator	private	protocol
public	static	struct	subscript
typealias	var

Keywords used in statements

break	case	continue	default
do	else	fallthrough	for
if	in	return	switch
where	while

Keywords used in expressions and types

as	dynamicType	false	is
nil	self	Self	super
true	_COLUMN_	_FILE_	_FUNCTION_
_LINE_

Keywords used in particular contexts

associativity	convenience	dynamic	didSet
final	get	infix	inout
lazy	left	mutating	none
nonmutating	optional	override	postfix
precedence	prefix	Protocol	required
right	set	Type	unowned
weak	willSet

Whitespaces

A line containing only whitespace, possibly with a comment, is known as a blank line, and a Swift compiler totally ignores it.

Whitespace is the term used in Swift to describe blanks, tabs, newline characters, and comments. Whitespaces separate one part of a statement from another and enable the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement −

var age

there must be at least one whitespace character (usually a space) between var and age for the compiler to be able to distinguish them. On the other hand, in the following statement −

int fruit = apples + oranges   //get the total fruits

no whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some for better readability.

Literals

A literal is the source code representation of a value of an integer, floating-point number, or string type. The following are examples of literals −

92               // Integer literal

4.24159      // Floating-point literal

"Hello, World!"  // String literal