Control flow with if, switch, and loops | Swift

Control flow lets a program choose what to do. Swift uses familiar tools: if, else, switch, for-in, and while.

if and else

Use if when code should run only when a condition is true:

let temperature = 34

if temperature <= 32 {
    print("Freezing")
} else {
    print("Above freezing")
}

Conditions must be booleans. Swift does not treat 0, empty strings, or empty arrays as false.

switch

Use switch when a value can be handled in several distinct ways:

let statusCode = 404

switch statusCode {
case 200:
    print("OK")
case 400..<500:
    print("Client error")
case 500..<600:
    print("Server error")
default:
    print("Unknown response")
}

Swift switch statements must be exhaustive. Every possible value must be handled, either by specific cases or by default. That requirement pushes you to think through states instead of ignoring them.

guard for early exits

guard is used when code cannot continue unless a condition is true:

func showProfile(username: String) {
    guard !username.isEmpty else {
        print("Missing username")
        return
    }

    print("Loading profile for \(username)")
}

This keeps the successful path less nested. You will use guard often with optionals.

Loops

Use for-in to iterate over a sequence:

let names = ["Ava", "Noah", "Mia"]

for name in names {
    print(name)
}

Use while when repetition depends on a condition:

var attempts = 0

while attempts < 3 {
    attempts += 1
}

What to carry forward

if handles simple branches
switch handles multiple known cases and must be exhaustive
guard exits early when required conditions fail
for-in loops over collections and ranges
while repeats while a condition stays true

Next, you will package reusable work into functions.