← Back to Swift Course | Chapter 3: Control Flow | Lesson 1 of 8

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:

  1. Basic if Statement
  2. if-else
  3. else if Chains
Syntax
swift 
if condition {
    // runs when true
} else if otherCondition {
    // runs when this is true
} else {
    // fallback
}

Basic if Statement

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

Example: Basic if Statement

markup 
// Declare a constant `temperature`, set to `30`
let temperature = 30
// Check whether `temperature > 25`
if temperature > 25 {
    // Print "It is hot outside" to the console
    print("It is hot outside")
}

if-else

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

Example: if-else

markup 
// Declare a constant `temperature`, set to `15`
let temperature = 15
// Check whether `temperature > 25`
if temperature > 25 {
    // Print "It is hot outside" to the console
    print("It is hot outside")
// Otherwise, run this branch
} else {
    // Print "It is not that hot" to the console
    print("It is not that hot")
}

else if Chains

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

markup 
// Declare a constant `score`, set to `72`
let score = 72
// Check whether `score >= 90`
if score >= 90 {
    // Print "Grade: A" to the console
    print("Grade: A")
// Otherwise, if `score >= 70`, run this branch
} else if score >= 70 {
    // Print "Grade: B" to the console
    print("Grade: B")
// Otherwise, run this branch
} else {
    // Print "Grade: C or below" to the console
    print("Grade: C or below")
}
Related Topics

The guard Statement · Switch Statement Basics · The for-in Loop · while and repeat-while Loops

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Common Mistakes
  1. Wrapping the condition in parentheses like if (x > 5), which is unnecessary and not idiomatic Swift (though harmless).
  2. Forgetting the curly braces around a single-statement body; Swift requires them, unlike some C-style languages.
  3. 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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