Swift - Basic Syntax

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If the Swift is installed successfully it will show the latest version of Swift. Swift is a powerful and expressive language to develop applications for Apple’s devices. It is designed to be easy to read, write and maintain. It also supports object-oriented and functional programming paradigms.

Syntax

Its syntaxes are much more clear, concise and easy to read. Now let us now see the basic structure of a Swift program, so that it will be easy for you to understand the basic building blocks of the Swift programming language.

/* My first Swift program */
var myString = "Hello, World!"

print(myString)

Following is the output of the above program −

Hello, World!

Now let us learn what are the basic syntaxes and how you can use them in your Swift program.

Import Statement

You can use the import statement to import any Objective-C framework or C library) or Swift library directly into your Swift program. For example, the 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.

Syntax

Following is the syntax of the import statement −

import frameworkName or LibraryName

Example

import Foundation

Tokens

A Swift program consists of various tokens. A token is the smallest unit of the program which is used to build the blocks of Swift programs. They can be either a keyword, an identifier, a constant, a string literal, or a symbol.

Example

Swift program to demonstrate the use of tokens. Here the program contains 10 tokens such as import, Foundation, var, myString, etc.

import Foundation
var myString = 34
print(myString)

Output

34

Semicolons

In Swift, semicolons after each statement are optional. It is totally up to your choice whether you want or not to type a semicolon (;) after each statement in your code, the compiler does not complain about it.

However, if you are using multiple statements in the same line, then it is required to use a semicolon as a delimiter, otherwise, the compiler will raise a syntax error.

Example

Swift program to demonstrate the use of semicolons in a single line.

// Separating multiple statements using semicolon
var myString = "Hello, World!"; print(myString)

Output

Hello, World!

Identifiers

A Swift identifier is a name used to identify a variable, function, or any other user-defined item. An identifier name must start with the 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, so Manpower and manpower are two different identifiers in Swift.

Example

Following are some valid identifiers in Swift −

Azad       zara    abc   move_name  a_123
myname50   _temp   j     a23b9      retVal

Keywords

Keywords are the special pre-defined words available in Swift that have some special meaning and functionality. They are also known as reserved words. These reserved words may not be used as constants, variables or any other identifier names unless they're escaped with backticks(`).

For example, class is not a valid identifier, but `class` is valid. They are commonly designed to define the structure and behaviour of the programs. Swift supports the following keywords −

Keywords used in declarations

The following are Keywords used in declarations

Keywords used in statements

The following are Keywords used in statements

Keywords used in expressions and types

The following are Keywords used in expressions and types

Keywords used in particular contexts

The following are Keywords used in particular contexts

Whitespaces

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:

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

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

Space on both sides of an operator should be equal, for example −

int fruit= apples +oranges   //is a wrong statement
int fruit = apples + oranges   //is a Correct statement

Literals

A literal is the source code representation of a value of an integer, floating-point number, or string type. Or we can say that literals are the actual values that are directly written in the source code. Swift supports integer literals, floating-point literals, String literals, boolean literals, etc.

Example

Following is the examples of literals −

92               	// Integer literal
4.24159          	// Floating-point literal
"Hello, World!"  	// String literal

Printing in Swift

In Swift, you can print anything to the console using the print() function. It is the most useful function in Swift language. It can also print files, functions and line numbers.

Syntax

Following is the syntax of the print() function −

func print(_element: Any…, Sep: String = “ “, Terminator: String = “\n”)

Parameters

This function takes only three parameters and they are optional −

• Element − It is the element that we want to print as output in the console. It can be zero or more.

• Sep − It represents a string that will be displayed between each element. By default, it takes a single space.

• Terminator − It represents a string that will print after all the elements. By default, its value is a newline. We can give our custom separators and terminators according to our requirements.

Example

Swift program to demonstrate how to print text using print() function.

import Foundation

// Printing text
print("Learn Swift!")

// Printing variables
var x = 10
var y = 23
print("[\(x) and \(y)]")

// Printing text with terminator
print("Swift, Programming Language", terminator: "*")
print("Swift Programming Language")

Output

Learn Swift!
[10 and 23]
Swift, Programming Language*Swift Programming Language