1. Introduction

Strings in Swift are a sequence of characters and are used to store textual data. Swift provides a robust set of methods and properties to efficiently work with and manipulate strings.

2. Source Code Example

// 1. Declaring a string let helloWorld = "Hello, world!" // 2. Accessing characters for character in helloWorld { print(character) } // 3. Concatenate strings let firstName = "John" let lastName = "Doe" let fullName = firstName + " " + lastName print(fullName) // 4. Interpolating strings let age = 30 let introduction = "My name is \(firstName) and I am \(age) years old." print(introduction) // 5. Checking string emptiness let emptyString = "" if emptyString.isEmpty { print("The string is empty!") } // 6. Count characters in a string let count = helloWorld.count print("Number of characters in '\(helloWorld)' is \(count)") // 7. String comparison if firstName == "John" { print("\(firstName) is indeed John!") } // 8. String methods let uppercaseString = firstName.uppercased() print(uppercaseString) let lowercaseString = "HELLO".lowercased() print(lowercaseString) 

Output:

H e l l o , w o r l d ! John Doe My name is John and I am 30 years old. The string is empty! Number of characters in 'Hello, world!' is 13 John is indeed John! JOHN hello 

3. Step By Step Explanation

1. Declaring a String: Here, a constant string helloWorld is declared with the text "Hello, world!".

2. Accessing Characters: Strings in Swift are collections of characters. You can iterate over each character in a string using a for-in loop.

3. Concatenate Strings: Strings can be concatenated using the + operator. In the example, firstName and lastName are combined to produce fullName.

4. Interpolating Strings: String interpolation allows you to insert variables directly into a string using the \(variable) syntax.

5. Checking String Emptiness: The isEmpty property checks if the string is empty or not.

6. Counting Characters: The count property gives the number of characters in a string.

7. String Comparison: Strings can be compared for equality using the == operator.

8. String Methods: The uppercased() method converts a string to uppercase and the lowercased() method converts a string to lowercase.