If-Else Statements

An if-else statement lets your program make a decision, like choosing one path if something is true and another path if it's not.

In this page:

An if statement runs its block of code only when the condition inside the parentheses-free header evaluates to true.

Example: Basic if Statement

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let temperature = 30
if temperature > 25 {
    print("It is hot outside")
}

Adding an else clause provides a fallback block that runs when the if condition is false.

Example: if-else

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let temperature = 15
if temperature > 25 {
    print("It is hot outside")
} else {
    print("It is not that hot")
}

Multiple conditions can be checked in order using else if, stopping at the first one that is true.

Note: Swift requires curly braces around every branch body, even a single-line one.

Example: else if Chains

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let score = 72
if score >= 90 {
    print("Grade: A")
} else if score >= 70 {
    print("Grade: B")
} else {
    print("Grade: C or below")
}

Common Mistakes

Wrapping the condition in parentheses like if (x > 5), which is unnecessary and not idiomatic Swift (though harmless).
Forgetting the curly braces around a single-statement body; Swift requires them, unlike some C-style languages.
Chaining many separate if statements when a single else if chain (or switch) would be clearer.

Chapter Summary

if executes a block only when its condition is true.
else if checks additional conditions in sequence, and else runs when none matched.
Curly braces { } are mandatory in Swift, even for a single statement.
Conditions must be actual Bool expressions -- Swift will not accept an Int as a condition.

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