Swift String Length (How to Count the Number of Characters)

To get the length of a string in Swift, call the String.count property.

For example:

let myStr = "This is a test"
let length = myStr.count

print(length)

Output:

14

Replace ‘count’ with ‘length’ in Swift

Swift developers decided to call the length of a string ‘count’. However, if you prefer ‘length’ over ‘count’ you can change it by writing an extension to the String class.

Naively, you could write a method that accesses the count of the string:

extension String {
    func length() -> Int {
        return self.count
    }
}

But this would mean you have to call the length with a set of parenthesis, unlike count.

let myStr = "Hello, world"
print(myStr.length())

If you would like to call String.length without parenthesis similar to String.count, you can write an extension that utilizes computed properties.

Here is how to do it:

extension String {
    var length: Int {
        return self.count
    }           
}

Now it is possible to call String.length on any Swift string:

let myStr = "Hello, world"
print(myStr.length)

Output:

12

Timeline of Swift String Length

Swift 1.1

In Swift 1.1, counting characters of a string was possible using the countElements() function. This function returned the number of elements in a collection, such as a string:

let myStr = "Hello, world"
let length = countElements(myStr)

print(length)

Output:

12

Swift 1.2

In Swift 1.2 you could count the number of letters in a string with a count() function:

let myStr = "Hello, world"
let length = count(myStr)

print(length)

Output:

12

Swift 2.0

In Swift 2.0, the count() function was removed and was replaced by a member function String.characters.count.

For example:

let myStr = "Hello, world"
let length = myStr.characters.count

print(length)

Output:

12

Swift 4.2+

As of Swift 4.2, to get the length of a string, access the String.count member.

For example:

let myStr = "Hello, world"
let length = myStr.count

print(length)

Output:

12

Tip of the Day – String.isEmpty

If you need to find out if a string has exactly 0 characters, you could check String.count is 0:

let myStr = ""

if myStr.count == 0 {
    // Do something
}

But you can do this more conveniently by accessing the isEmpty property:

let myStr = ""

if myStr.isEmpty {
    // Do something
}