**Course Title:** Swift Programming: From Basics to Advanced Development **Section Title:** Control Flow and Functions **Topic:** Loops: for-in, while, repeat-while Welcome to this topic on loops in Swift. Loops are an essential part of programming that allow you to execute a block of code repeatedly. In the previous topics, you learned about conditional statements. Now, you will learn about the different types of loops available in Swift. ### 1. For-in Loops A for-in loop is used to iterate over a sequence, such as an array, dictionary, or string. It's a powerful and easy-to-use loop that allows you to access each element in the sequence. ```swift // Example of a for-in loop with an array let fruits = ["Apple", "Banana", "Orange"] for fruit in fruits { print(fruit) } // Example of a for-in loop with a dictionary let person = ["name": "John", "age": 30, "city": "New York"] for (key, value) in person { print("\(key): \(value)") } ``` In the first example, the for-in loop iterates over the `fruits` array and prints each element. In the second example, the for-in loop iterates over the `person` dictionary and prints each key-value pair. ### 2. While Loops A while loop is used to execute a block of code as long as a certain condition is met. It's a more flexible loop than the for-in loop, but it requires you to manually increment the loop counter. ```swift // Example of a while loop var count = 0 while count < 5 { print("\(count)") count += 1 } ``` In this example, the while loop executes as long as the `count` variable is less than 5. Inside the loop, we increment the `count` variable by 1. ### 3. Repeat-while Loops A repeat-while loop is similar to a while loop, but it guarantees that the loop body will be executed at least once. The condition is checked after the loop body has been executed. ```swift // Example of a repeat-while loop var count = 0 repeat { print("\(count)") count += 1 } while count < 5 ``` In this example, the repeat-while loop executes as long as the `count` variable is less than 5. Inside the loop, we increment the `count` variable by 1. **Key Concepts:** * Loops are used to execute a block of code repeatedly. * For-in loops are used to iterate over sequences. * While loops and repeat-while loops are used to execute a block of code as long as a certain condition is met. * Loops can be used to solve a variety of problems, such as iterating over data structures or repeatedly executing a block of code. **Practical Takeaways:** * When working with sequences, use for-in loops to simplify your code and make it more readable. * When working with conditions, use while loops or repeat-while loops to execute a block of code repeatedly. * Always use a conditional statement to control the loop and prevent infinite loops. **Example Use Cases:** * Iterating over an array of numbers to calculate the sum. * Iterating over a dictionary to retrieve values. * Repeatedly executing a block of code while a certain condition is met. **External Resources:** * [Swift Documentation: Control Flow](https://docs.swift.org/swift-book/ReferenceManual/Statements.html) * [Swift by Tutorials: Loops](https://www.raywenderlich.com/5529333-swift-4-control-flow) **Do you need help with anything?** Please ask your instructor by leaving a comment below. **Key terms we will be covering in the next topic:** * Functions * Parameters * Return values * Function types Please proceed to the next topic, "Creating and using functions: parameters, return values, and function types," to learn more about functions in Swift.