Control flow

Control flow in Swift refers to the mechanisms used to control the sequence of events or the flow of execution in a program. Swift provides various control flow constructs like loops, conditionals, and branches.

Conditional Statements

If Statement

The if statement is used to conditionally execute a block of code.

let x = 10
if x > 5 {
   print("x is greater than 5")
}

If-Else Statement

You can use the else clause to execute code when the condition is not met.

if x > 5 {
   print("x is greater than 5")
} else {
   print("x is less than or equal to 5")
}

If-Else If-Else Statement

You can chain multiple if conditions using else if.

if x > 10 {
   print("x is greater than 10")
} else if x > 5 {
   print("x is greater than 5 but less than or equal to 10")
} else {
   print("x is less than or equal to 5")
}

Switch Statement

Swift's switch statement is powerful and can match against a variety of conditions, including ranges and tuples.

switch x {
case 0:
   print("Zero")
case 1...9:
   print("Single digit")
case 10:
   print("It's ten")
default:
   print("More than ten")
}

Loops

For-In Loop

Used for iterating over sequences like arrays, dictionaries, ranges, etc.

for i in 1...3 {
   print(i)
}
for element in [1, 2, 3] {
   print(element)
}
for (key, value) in ["One": 1, "Two": 2] {
   print("\(key): \(value)")
}

While Loop

Executes a block of code as long as a condition is true.

var i = 1
while i <= 3 {
   print(i)
   i += 1
}

Repeat-While Loop

Similar to the while loop but evaluates the condition after executing the code block, guaranteeing at least one execution.

var i = 1
repeat {
   print(i)
   i += 1
} while i <= 3

Control Transfer Statements

Continue

Used within a loop to skip the current iteration.

for i in 1...5 {
   if i == 3 {
       continue
   }
   print(i)
}

Break

Used to exit a loop or a switch statement immediately.

for i in 1...5 {
   if i == 3 {
       break
   }
   print(i)
}

Labeled Statements

You can label loops and conditional statements, and then use break or continue with those labels for better control.

outerLoop: for i in 1...3 {
   for j in 1...3 {
       if j == 2 {
           break outerLoop
       }
       print("\(i), \(j)")
   }
}

Fallthrough

In Swift, switch cases don't fall through by default. Use the fallthrough keyword to achieve C-style fallthrough behavior.

switch x {
case 10:
   print("It's ten")
   fallthrough
case 1...9:
   print("Single digit")
default:
   print("More than ten")
}

These are the fundamental control flow constructs in Swift, allowing for powerful and flexible programming.