Swift Characters and Strings

Swift Character

Character is a data type that represents a single-character string ("a", "@", "5", etc).

We use the Character keyword to create character-type variables in Swift. For example,

var letter: Character

Here, the letter variable can only store single-character data.

Character Example

// create character variable
var letter: Character = "H"
print(letter)  // H

var symbol: Character = "@"
print(symbol)  // @ 

In the above example, we have created two character variables: letter and symbol. Here, we have assigned "H" to letter and "@" to symbol.

// create character variable
let test: Character = "H@" 

print(test)

// Error:
// cannot convert value of type 'String' to specified type Character

Swift String

In Swift, a string is used to store textual data ("Hey There!", "Swift is awesome.", etc).

We use the String keyword to create string-type variables. For example,

let name: String

Here, the name variable can only store textual data.

Note: Since a string contains multiple characters, it is called a sequence of characters.

String Example

// create string type variables

let name: String = "Swift"
print(name)

let message = "I love Swift."
print(message) 

Output

Swift
I love Swift.

In the above example, we have created string-type variables: name and message with values "Swift" and "I love Swift" respectively.

Notice the statement,

let message = "I love Swift."

Here, we haven't used the String keyword while creating the variable. It is because Swift is able to infer the type based on the value.

Note: In Swift, we use double quotes to represent strings and characters.

String Operations

The String class in Swift provides various built-in functions that allow us to perform different operations on strings.

1. Compare Two Strings

We use the == operator to compare two strings. If two strings are equal, the operator returns true. Otherwise, it returns false. For example,

let str1 = "Hello, world!"
let str2 = "I love Swift."
let str3 = "Hello, world!"

// compare str1 and str2
print(str1 == str2)

// compare str1 and str3
print(str1 == str3)

Output

false
true

In the above example,

• str1 and str2 are not equal. Hence, the result is false.
• str1 and str3 are equal. Hence, the result is true.

2. Join Two Strings

We use the append() function to join two strings in Swift. For example,

var greet = "Hello "
var name = "Jack"

// using the append() method
greet.append(name)
print(greet)

Output

Hello Jack

In the above example, we have used the append() method to join name and greet.

Concatenate Using + and +=

We can also use the + and += operators to concatenate two strings.

var greet = "Hello, "
let name = "Jack"

// using + operator
var result = greet + name
print(result)

//using =+ operator
greet +=  name
print(greet)

Output

Hello, Jack
Hello, Jack

In the above example, we have used the + and += operators to join two strings: greet and name.

Note: We cannot create greet using let. It is because the += operator joins two strings and assigns the new value to greet.

3. Find Length of String

We use the count property to find the length of a string. For example,

let message = "Hello, World!"

// count length of a string
print(message.count) // 13

Note: The count property counts the total number of characters in a string including whitespaces.

Other Built-in Functions

Escape Sequences

The escape sequence is used to escape some of the characters present inside a string.

Suppose we need to include double quotes inside a string.

// include double quote
var example = "This is "String" class"

print(example) // throws error

Since strings are represented by double quotes, the compiler will treat "This is " as the string. Hence, the above code will cause an error.

To solve this issue, we use the escape character \ in Swift.

// use the escape character
var example = "This is \"String\" class"

print(example)

// Output: This is "String" class

Now the program will run without any error. Here, the escape character will tell the compiler to ignore the character after \.

Here is a list of all the escape sequences supported by Swift.

String Interpolation

We can also use the backslash character \ to use variables and constants inside a string. For example,

let name = "Swift"

var message = "This is \(name) programming."
print(message)

Output

This is Swift programming.

In the above example, notice the line

var message = "This is \(name) programming."

Here, we are using the name variable inside the string message. This process is called String Interpolation in Swift.

Swift Multiline String

We can also create a multiline string in Swift. For this, we use triple double quotes """. For example,

// multiline string 
var str: String = """
Swift is awesome
I love Swift
"""

print(str)

Output

Swift is awesome
I love Swift

In the above example, anything inside the enclosing triple-quotes is one multiline string.

// error code
var str = """Swift 
I love Swift
"""

Create String Instance

We can also create a string using an initializer syntax. For example,

var str = String()

Here, the initializer syntax String() will create an empty string.