Does Swift have a Trim Method for Strings?

In Swift, you can use the trimmingCharacters(in:) method of the String type to trim parts of a string. It is an instance method that returns a newly created string made by removing the applied character set.

This method accepts a parameter of type CharacterSet to perform leading and trailing characters. You can apply different types of CharacterSet to trim a string.

There are some of the most commonly used CharacterSets, like −

• whitespaces

• whitespacesAndNewlines

• decimalDigits

• letters

• lowercaseLetters

• uppercaseLetters

• punctuationCharacters

• capitalizedLetters

• newlines

You will learn some of them about how to perform different types of trimming of a string.

Whitespaces

Syntax

It is used to remove leading and trailing whitespaces from a string. For example,

trimmingCharacters(in: .whitespaces)

Example

You have to call the trimmingCharacters instance method of the string with the whitespaces CharacterSet.

import Foundation
let sentence = "  this is a sample string containing leading and trailing spaces    "
let trimmedString = sentence.trimmingCharacters(in: .whitespaces)
print("trimmed string: \(trimmedString)")

Output

trimmed string: this is a sample string containing leading and trailing spaces

WhitespacesAndNewlines

Syntax

It is used to remove leading and trailing spaces along with newline characters from a string.

let sentence = "   \n this is a sample string containing newlines, leading and trailing spaces    "

Example

This is the string you need to trim leading and trailing spaces and newlines. First, we will trim it by whitespace CharacterSet and then by whitespacesAndNewlines so that you can understand it in a better way.

import Foundation
let sentence = "   \n this is a sample string containing newlines, leading and trailing spaces    "
let trimmedString = sentence.trimmingCharacters(in: .whitespaces)
print("trimmed string: \(trimmedString)")

Output

trimmed string: 
 this is a sample string containing newlines, leading and trailing spaces

Example

You can see, the leading and trailing whitespaces are trimmed but the newlines are not removed. In order to trim both things at once, you need to use the whitespacesAndNewlines CharacterSet.

import Foundation
let sentence = "   \n this is a sample string containing newlines, leading and trailing spaces    "
let trimmedString = sentence.trimmingCharacters(in: .whitespacesAndNewlines)
print("trimmed string: \(trimmedString)")

Output

trimmed string: this is a sample string containing newlines, leading and trailing spaces

DecimalDigits

Syntax

It is used to return a character set of decimal values from 0 to 9. For example,

trimmingCharacters(in: .decimalDigits)

Example

You have to call the trimmingCharacters instance method of the string with the decimalDigits CharacterSet.

import Foundation
let sentence = "16 is my lucky number same as 24"
let trimmedString = sentence.trimmingCharacters(in: .decimalDigits)
print("trimmed string: \(trimmedString)")

Output

trimmed string:  is my lucky number same as 

Example

How does it work with floating values?

import Foundation
let sentence = "1.6 is my lucky number same as 24"
let trimmedString = sentence.trimmingCharacters(in: .decimalDigits)
print("trimmed string: \(trimmedString)")

Output

trimmed string: .6 is my lucky number same as 

LowercaseLetters

Syntax

This CharacterSet returns a set of lowercase letters. For example,

trimmingCharacters(in: .lowercaseLetters)

Example

You have to call the trimmingCharacters instance method of the string with the lowercaseLetters CharacterSet.

import Foundation
let sentence = "this string is containing lowercase letters"
let trimmedString = sentence.trimmingCharacters(in: .lowercaseLetters)
print("trimmed string: \(trimmedString)")

Output

trimmed string:  string is containing lowercase 

As you can see, the leading and trailing lowercase letters have been removed from the string.

PunctuationCharacters

Syntax

This CharacterSet returns a set of punctuation characters. For example,

trimmingCharacters(in: .punctuationCharacters)

Example

You have to call the trimmingCharacters instance method of the string with the punctuationCharacters CharacterSet.

import Foundation
let sentence = ";this string is containing punctuation letters."
let trimmedString = sentence.trimmingCharacters(in: .punctuationCharacters)
print("trimmed string: \(trimmedString)")

Output

trimmed string: this string is containing punctuation letters

Newlinesm

Syntax

This CharacterSet returns a set of newline characters. For example,

trimmingCharacters(in: .newlines)

Example

You have to call the trimmingCharacters instance method of the string with the newlines CharacterSet.

import Foundation
let sentence = "\n\nthis \nstring is containing newlines characters\n"
let trimmedString = sentence.trimmingCharacters(in: .newlines)
print("trimmed string: \(trimmedString)")

Output

trimmed string: this 
string is containing newlines characters

You can see how to remove leading and trailing newline characters from a string.

Conclusion

The trimmingCharacters() method is the most essential method in the Swift language. Often, you need to perform different types of character trimming.