String

Strings in Swift are collections of characters, but they can be complicated to use. We cannot access characters just by integers. This allows strings to support a wide range of characters.

In this language, a for-loop allows us to access each individual character. We can test or count or these characters. The count property is often useful.

Simple example

Let us begin with a simple for-loop. The "c" variable here is the current iteration's character. We call print() on the characters.

let value = "cat"

// Loop over characters in string.
for c in value {
    print(c)
}
c
a
t

Count

This property returns the number of characters in the string. So with the string "carrot" it will return 6. The property cannot be assigned.

var vegetable = "carrot"

// Get count of chars in string.
let c = vegetable.count
print(c)
6

Contains

This method receives a Character, which can be specified as a one-char string. It returns true if the Character exists in the string, and false otherwise.

var vegetable = "turnip"

// The string contains this letter.
let n = vegetable.contains("n")
print(n)

// There is no "x" in the string.
let x = vegetable.contains("x")
print(x)
true
false

Count chars

To get the number of characters in a string, we can use count. All characters, including spaces and punctuation, are counted by this property.

// This string has four characters in it.
var value = "bird"
var length = value.count
print(length)

// This string has six characters.
// ... Spaces and other chars are all counted.
value = "x y z "
length = value.count
print(length)
4
6

IsEmpty

It is possible to test for an empty (zero-length) string by using the isEmpty property. This returns true if the count is zero.

// Demonstrate empty string.
let color = "";
if color.isEmpty {
    print("IS EMPTY");
}
IS EMPTY

Convert to String

A string may be created from a Character array. Here we create a Character array of six characters. When we convert it to a string, it equals the name "Sancho."

// Create a character array.
let chars: [Character] = ["S", "a", "n", "c", "h", "o"]

// Create a string from the character array.
let result = String(chars)
print(result)

// Test the string value.
if result == "Sancho" {
    print(true)
}
Sancho
true

Convert characters

We can apply UnicodeScalar to convert Ints into Characters. And with utf8 and utf16 we can access integral values in a string's character data.

We can directly access characters in a string. We can use this in a for-loop to test a string's text data. Other properties like count can also be useful.