Conditionals: if and else

A conditional runs code only when a condition is true.

Real-world analogy: "If it's raining, take an umbrella; otherwise, wear sunglasses."

Syntax

if condition {
    // runs when condition is true
} else if otherCondition {
    // runs when the first was false and this one is true
} else {
    // runs when none of the above were true
}

Example

let temperature = 18

if temperature > 25 {
    print("It's hot")
} else if temperature > 15 {
    print("It's pleasant")
} else {
    print("It's cold")
}

Expected output

It's pleasant

Swift checks the conditions from top to bottom and runs only the first branch that matches.

if as an expression

Since Swift 5.9, if can produce a value directly:

let age = 20
let status = if age >= 18 { "adult" } else { "minor" }
print(status)

adult

Combining conditions

let hour = 14
let isWeekend = false

if isWeekend || hour < 9 || hour >= 17 {
    print("Closed")
} else {
    print("Open")
}

Open

Common mistakes

• Leaving off the braces: if x > 5 print("big") doesn't compile. Braces are always required.
• Putting conditions in the wrong order. if score > 50 before if score > 90 means the second can never run.

Practice

Store an age and print adult for 18 and over, teen for 13–17, and child otherwise.

let age = 15

if age >= 18 {
    print("adult")
} else if age >= 13 {
    print("teen")
} else {
    print("child")
}

teen