Published by Arunprasadh C on 22 Apr 2022 • Last Updated on 02 May 2022

Basic Input and Output in Swift

Basic I/O Functions are used to print output to the standard output (usually console on the screen) and to get input from the standard input (usually provided through keyboard on the console). As in every other programming language, Swift too has its own set of I/O functions.

Output Function

Swift provides the print() function for printing output on the console. The print() function accepts three parameters. The prototype is as follows :

print(_ items: Any..., separator: String = " ", terminator: String = "\n")

• items - The variable argument object(s) of Any type to be printed.
• separator - The String to be used to separate multiple items while printing. The default value is a single whitespace " ".
• terminator - The String to be printed after printing the items. The default value is a newline escape sequence "\n".

Example 1 :

print("Hello World")

Output 1 :

Hello World

Example 2 :

var name = "Kris"
print("Good morning",name,separator: ",",terminator: " ")
print("!")

Output 2 :

Good morning,Kris !

Input Function

Swift uses a single function called readLine() for getting User Input from the Command Line. The readLine() function returns an Optional<String> as result. The value will be nil if no user Input was provided. The optional Bool argument strippingNewline strips away Newline Character \n if passed as true.

Example 1 :

print("Enter your name :")
var name = readLine() ?? "Anonymous"
print("Hello \(name) !")

When “Kris” is entered as Input, we get the following Output:

Output 1 :

Hello Kris !

If we want to get Int or any other Numerical Data Type input we need to first unwrap the result of readLine() and pass the String to the appropriate constructor.

Example 2 :

if let strVal = readLine(strippingNewline: true)
{
    let floatVal: Float = Float(strVal) ?? 0.0
    print("Float value : \(floatVal)")
    let intVal: Int = Int(floatVal)
    print("Int value : \(intVal)")
}
else
{
    fatalError("No User Input Provided !")
}

When “45.6” is entered as Input, we get the following Output:

Output 2 :

45.6
Float value : 45.6
Int value : 45

We can also get multiple inputs separated by some characters as input and split the resultant unwrapped String to access individual values and use them.

Example 3 :

var str = readLine() ?? ""
var elements = str.split(separator: ",")
var firstElement = Int(elements[0]) ?? 0
print("The first element is: \(firstElement) with type: \(type(of: firstElement))")

When “45,67,Hello” is entered as Input, we get the following Output:

Output 3 :

45,67,Hello
The first element is: 45 with type: Int

Now as we have seen about Basic I/O in Swift, we can move on to see about Operators in Swift.

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