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User Input in Swift commandline

Sun, 03 May 2020 22:18:51 -0700

Last Run on XCODE 11.4 / Swift 5.2

If you are writing a command line tool and need user input, the readLine() function can be used for it. It returns an optional

let input = readLine()

And, if you dont want the ending new line character, you can set the strippingNewline parameter to true.

let input = readLine(strippingNewline: true)

Checking if a Swift String contains a certain text

Fri, 01 May 2020 12:11:26 -0700

Last Run on XCODE 11.4 / Swift 5.2

A simple way to check if a string contains a certain text is to use the method contains available to Strings.

In the code snippet below, we will check if a string contains a certain text.

let fruit1 = "apple"
let fruit2 = "banana"
let mySentence = "An apple a day keeps the doctor away."

mySentence.contains(fruit1) // result --> True
mySentence.contains(fruit2) // result --> False

If we need to check the string against multiple options, we will have to use a variation of the contains method that takes a closure. Checkout the code snippet below.

Matching Swift Strings by Prefix or Suffix

Tue, 28 Apr 2020 21:56:43 -0700

Last Run on XCODE 11.4 / Swift 5.2

A simple way to check if a string starts or ends with a certain pattern is to use the method hasSuffix and hasPrefix available to Strings.

In the code snippet below, we will check if a string begins or ends with a specific text pattern.

let fileName1 = "InstagramCover.jpg"
let fileName2 = "SnapchatCover.doc"

fileName1.hasSuffix("jpg") // result --> True
fileName2.hasSuffix("jpg") // result --> False

fileName1.hasPrefix("Instagram") // --> True
fileName2.hasPrefix("Facebook") // result --> False

If we need to check against multiple variations, we can’t just use hasSuffix. Instead, we will have to use it along with another method contains. Checkout the code snippet below.

Access Swift String by Index

Tue, 21 Apr 2020 22:23:31 -0700

Last Run on XCODE 11.4 / Swift 5.2

The swift string class does not provide the ability to get a character at a specific index because of its native support for UTF characters.

In the code snippets below, we will walk through code to access elements of a string at speific positions.

Getting the first Character Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the first Character
mySwiftString.first

let firstIndex = mySwiftString.startIndex
mySwiftString[firstIndex]

Getting the last Character Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the last Character
mySwiftString.last

let lastIndex = mySwiftString.index(before: mySwiftString.endIndex)
mySwiftString[lastIndex]

Getting the 2nd Character Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the 2nd Character
let secondIndex_Ver1 = mySwiftString.index(after: firstIndex)
mySwiftString[secondIndex_Ver1]

let secondIndex_Ver2 = mySwiftString.index(firstIndex, offsetBy: 1)
mySwiftString[secondIndex_Ver2]

Getting the Nth Character from start ( Say 3rd) Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the Nth Character from start ( Say 3rd )
let thirdIndex = mySwiftString.index(firstIndex, offsetBy: 2)
mySwiftString[thirdIndex]

Getting the Nth Character from end ( Say 3rd last ) Link to heading

let mySwiftString = "Swift is awesome!"

//Getting the Nth Character from end ( Say 3rd last )
let thirdLastIndex = mySwiftString.index(lastIndex, offsetBy: -2)
mySwiftString[thirdLastIndex]