1. Introduction

This tutorial aims to introduce the concept of control flow structures in Swift programming language. Control flow structures allow your program to execute specific blocks of code based on a given condition or loop. It's a key concept to understand as it gives your code more flexibility and power.

By the end of this tutorial, you will learn about:
- If, Else If, and Else statements
- For and While loops
- Switch statements

Prerequisites: Basic understanding of Swift syntax and data types.

2. Step-by-Step Guide

If, Else If, Else Statements

An if statement checks whether a condition is true. If the condition is true, the code within the if statement is executed. If the condition is false, the code is skipped.

An else if statement follows an if or another else if statement and contains an additional condition that is checked if all preceding conditions are false.

An else statement follows an if or else if statement and is executed if all preceding conditions are false.

// If statement
var temperature = 20
if temperature < 30 {
    print("It's not too hot today.")
}

// Else If statement
var weather = "rainy"
if weather == "sunny" {
    print("It's a beautiful day.")
} else if weather == "rainy" {
    print("Don't forget your umbrella.")
}

// Else statement
var isSunny = false
if isSunny {
    print("It's a beautiful day.")
} else {
    print("It's cloudy.")
}

For and While Loops

A for loop executes a block of code a specific number of times.

A while loop executes a block of code as long as a condition is true.

// For loop
for i in 1...3 {
    print("Hello, Swift!")
}

// While loop
var number = 10
while number > 0 {
    print(number)
    number -= 1
}

Switch Statements

A switch statement checks a value and compares it against several possible matching patterns.

// Switch statement
var fruit = "apple"
switch fruit {
case "apple":
    print("Red and delicious.")
case "banana":
    print("Yellow and sweet.")
default:
    print("Unknown fruit.")
}

3. Code Examples

Let's see these concepts in action with more detailed examples:

Example 1: If, Else If, Else Statements

var score = 85

if score >= 90 {
    print("You got an A!")
} else if score >= 80 {
    print("You got a B!")
} else if score >= 70 {
    print("You got a C.")
} else {
    print("Better luck next time.")
}

This code evaluates a student's score and prints a grade. If the score is 90 or higher, the student gets an A. If the score is less than 90 but 80 or higher, the student gets a B, and so on.

Example 2: For and While Loops

// For loop
for number in 1...5 {
    print("Number is: \(number)")
}

This code prints numbers 1 through 5. It uses a for loop to iterate over a range.

// While loop
var count = 1
while count <= 5 {
    print("Count is: \(count)")
    count += 1
}

This code does the same thing as the previous example, but it uses a while loop.

Example 3: Switch Statements

var dayOfWeek = "Tuesday"

switch dayOfWeek {
case "Monday", "Wednesday", "Friday":
    print("Gym day.")
case "Tuesday", "Thursday":
    print("Rest day.")
default:
    print("Free day.")
}

This code prints an activity based on the day of the week.

4. Summary

In this tutorial, we covered control flow structures in Swift, including if, else if, else statements, for and while loops, and switch statements. Control flow structures are a fundamental part of any programming language and provide flexibility in code execution.

Continuing to practice these concepts with different scenarios will lead to a better understanding. You can also explore more advanced topics like nested loops and switch statements with ranges.

5. Practice Exercises

Exercise 1: Write a Swift program that prints the multiplication table of 5 using a for loop.

Exercise 2: Write a Swift program that counts down from 10 to 1 using a while loop.

Exercise 3: Write a Swift program that categorizes a given number into "positive", "negative", or "zero" using a switch statement.

Solutions:

// Exercise 1
for i in 1...10 {
    print("5 * \(i) = \(5 * i)")
}

// Exercise 2
var number = 10
while number > 0 {
    print(number)
    number -= 1
}

// Exercise 3
var number = 0
switch number {
case let x where x > 0:
    print("Positive")
case let x where x < 0:
    print("Negative")
default:
    print("Zero")
}

Keep practicing these exercises with different inputs and scenarios to get a solid understanding of control flow structures in Swift. Happy coding!