Swift Control Flow

Control flow in Swift allows developers to dictate the order in which code statements are executed. It includes conditional statements (if, guard, switch) for making decisions based on conditions, and looping statements (for-in, while, repeat-while) for repeating code blocks until a condition is met or satisfied.

Key Concepts:

1. Conditional Statements:

   • if Statement: Executes a block of code if a condition is true.

     let number = 10
     if number > 0 {
         print("Number is positive")
     } else {
         print("Number is non-positive")
     }

   • guard Statement: Provides an early exit from a function if a condition isn’t met.

     func process(number: Int?) {
         guard let number = number else {
             print("Number is nil")
             return
         }
         print("Number is \(number)")
     }
     process(number: 42) // Output: Number is 42

   • switch Statement: Evaluates a value against multiple possible matching patterns.

     let grade = "A"
     switch grade {
         case "A":
             print("Excellent!")
         case "B", "C":
             print("Good")
         default:
             print("Need improvement")
     }

2. Looping Statements:

   • for-in Loop: Iterates over a sequence (e.g., array, range) of items.

     let names = ["Alice", "Bob", "Charlie"]
     for name in names {
         print("Hello, \(name)!")
     }

   • while Loop: Executes a block of code repeatedly as long as a condition is true.

     var counter = 5
     while counter > 0 {
         print("Counter: \(counter)")
         counter -= 1
     }

   • repeat-while Loop: Similar to while, but ensures the block of code is executed at least once before checking the condition.

     var attempts = 0
     repeat {
         print("Attempt \(attempts)")
         attempts += 1
     } while attempts < 3

3. Control Transfer Statements:

   • break: Terminates the execution of a loop or switch statement.
   • continue: Skips the current iteration of a loop and proceeds to the next iteration.
   • fallthrough: Used in a switch statement to fall through to the next case.

Example:

// Example combining conditional and looping statements
let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
var sum = 0

for number in numbers {
    if number % 2 == 0 {
        continue // Skip even numbers
    }
    
    if number > 5 {
        break // Stop processing when number exceeds 5
    }
    
    sum += number
}

print("Sum of odd numbers less than or equal to 5: \(sum)") // Output: Sum of odd numbers less than or equal to 5: 9

Key Concepts Demonstrated:

• Combining Statements: The example demonstrates using for-in loop to iterate over an array, using if statements for conditions (continue and break), and accumulating a sum based on specific conditions.
• Control Transfer: continue skips even numbers, break stops processing when a condition is met, showing how control flow statements alter program execution.